Is this a horribly ambiguous A Level Physics question?

[ChrisXenon]

Hi, I'm a private tutor who is not a school teacher and has no contact with schools.

I have an OCR A level "physics A" student, and we're working through past papers. Time and time again, we've come across questions which are astonishingly ambiguous and answer schemes which are in my view, astonishingly picky or just plane bizarre. I've taken some of these to OCR but got no progress.

For example they maintain that the word "rate" implies an increasing quantity, whereas I believe that "rate of pay" simply means how much you get paid. They say that "acceleration" will not do when a body is decelerating whereas I think that "deceleration" is an acceleration with a negative value and that all decelerations are accelerations.

We can't agree, but I'm not convinced I'm wrong, so I am looking for broader perspectives. If I AM wrong, then I need to know it and change my teaching accordingly. If I AM NOT wrong, then there's is something very worrying about how we measure OCR physics A level candidates.

So I'm looking for insights from teachers or physics experts.

Here is an example from yesterday's lesson. OCR Physics A H156/01 May 2016, Q27. A graph shows an I/V curve for an LED whose threshold voltage is 2.7V.

Question a: Describe and justify the variation of resistance R of the LED as the potential difference V across the LED is increased from:
(i) -1.0V to 2.6V
(ii) 2.6V to 3.0V
(iii) 3.0V to 3.4V

- but what does it mean by "and justify"?

I thought it meant "explain in terms of semiconductor behaviour", and - without prompting - my student thought the same. But in fact, the answer scheme makes clear that it wants stuff like "R is infinite because R = V/I = 2.9 / 0". OK but what is required is simply not clear from the question which in my view is horribly ambiguous. Both my student and I would have scored no points for that question. And these instances arise in every paper and sometimes more than once.

Relating to this - how do marking schemes work in practice; are they adhered to as the letter of the law or are they taken with a pinch of salt and markers go with "the right answer" as they see it. Actually either is worring but for different reasons.

So - any insights you can offer, on this question in particular, or the examples above it, or on exam querstions & marking - would be very welcome.

Thanks

 

[phinds]

For example they maintain that the word "rate" implies an increasing quantity, whereas I believe that "rate of pay" simply means how much you get paid. They say that "acceleration" will not do when a body is decelerating whereas I think that "deceleration" is an acceleration with a negative value and that all decelerations are accelerations.

You are correct on both counts and I also agree with your analysis of the other problem you mentioned.

I've often found this kind of idiocy on "standardized" tests, which often seem to have been formulated by bureaucrats, not teachers.

 

[Mark44]

For example they maintain that the word "rate" implies an increasing quantity, whereas I believe that "rate of pay" simply means how much you get paid. They say that "acceleration" will not do when a body is decelerating whereas I think that "deceleration" is an acceleration with a negative value and that all decelerations are accelerations.

Regarding rates, they usually mean how some quantity is changing relative to some other quantity, where the "other quantity" is often time, but could be something other than time. In your example, "pay rate" is not just how much you get paid -- there is an implied time period. If my hourly pay rate is $30, this rate is actually $\frac{30}{\text{hour}}$.
Regarding acceleration, I agree that acceleration could be negative, zero, or positive, but if the question specifically asks whether an object is accelerating or decelerating, and a < 0, then the correct answer would be "decelerating," IMO.

 

[phinds]

If my hourly pay rate is $30, this rate is actually $\frac{30}{\text{hour}}$.

But that's not an "increasing quantity" which is what he asked about

Regarding acceleration, I agree that acceleration could be negative, zero, or positive, but if the question specifically asks whether an object is accelerating or decelerating, and a < 0, then the correct answer would be "decelerating," IMO.

fair point.

 

[Mark44]

But that's not an "increasing quantity" which is what he asked about

The salary/wage paid is increasing -- at a rate of $30/hour in my example.

 

[ChrisXenon]

But that's not an "increasing quantity" which is what he asked about
fair point.

Guys thanks for your comments so far. Mark44 - thanks - you have helped me to understand what the OCR question-setter was saying.

In that case, the marking scheme forbade the term "rate of acceleration". In that context I still see the point but I feel it is very weak. When someone says "rate of acceleration" I take it to mean the rate of change of veolicty with time.

I think this may be a case where tying down words so specifically can impede the freedom od markers to behave intellignelty. Of course physics is a world where language must be used carefully to precisely express concepts and demonstrating understanding must be done through the written word so care is mandatory but in my view, this stipulation is wrong.

Interestingly, in the next part of that question "rate" is allowed. They felt is was unfair to penalise it's incorrect usage twice.

Actually (and rhetorically, maybe) if we think rate means change then why do we so often say "rate of change"?

 

[ChrisXenon]

For completeness, in case anyone's interested, here is the complete context of the "rate" question as originally sent to OCR:

A velocity/time graph shows an upward-curving line between t=0 & 2, and a straight descending line between 4=2 & 7. The question invites the student to describe the motion of the object.

That seems clear enough until you see the answer scheme. Two things puzzle me:

1. It FORBIDS any answers using "rate of acceleration". Please explain why. Later on (Q2a), you accept that same term. What is wrong with it?

2. Part 2 FORBIDS "constant acceleration". Why? The term "deceleration" is accepted, but any constant deceleration is also a constant acceleration whose magnitude is negative; it's still an acceleration. If I toss a ball into the air and consider its vertical velocity, we can note that it will have an initial upwards velocity (which we can arbitrarily label "positive"). It will slow down, then stop, then change direction and velocity will increase in the negative direction. If we plot its vertical velocity over that time, we'll see those velocities move from positive, through zero, to negative. Throughout this period the acceleration is a constant - g. So it has sped up, stopped, changed direction and sped up again, but it's perfectly correct to say it's ACCELERATION was constant, and it would be odd to say its DECELERATION was anything.

 

[phinds]

The salary/wage paid is increasing -- at a rate of $30/hour in my example.

? that's not what you said.

In your example, "pay rate" is not just how much you get paid -- there is an implied time period. If my hourly pay rate is $30, this rate is actually $\frac{30}{\text{hour}}$.

I think an increasing rate of pay would be when you get a raise, but I sort of see how you are looking at it. You are considering that the PAY is increasing, not that the RATE of pay is increasing.

 

[vela]

Question a: Describe and justify the variation of resistance R of the LED as the potential difference V across the LED is increased from:
(i) -1.0V to 2.6V
(ii) 2.6V to 3.0V
(iii) 3.0V to 3.4V

- but what does it mean by "and justify"?

I thought it meant "explain in terms of semiconductor behaviour", and - without prompting - my student thought the same. But in fact, the answer scheme makes clear that it wants stuff like "R is infinite because R = V/I = 2.9 / 0". OK but what is required is simply not clear from the question which in my view is horribly ambiguous. Both my student and I would have scored no points for that question. And these instances arise in every paper and sometimes more than once.

Justify means you need to explain how you got the answer. Many students may be able to tell you the resistance is effectively infinite below the threshold voltage, but if you were to ask them why it is so, they'll say, "I don't know," because all they did was memorize a result without understanding the reasoning behind it.

As to what level of justification is appropriate, that's a part of the art of test-taking. Frankly, given the question, I think your interpretation of explaining in terms of semiconductor behavior would be overkill, but you know the test better than I do.

 

[Mark44]

The salary/wage paid is increasing -- at a rate of $30/hour in my example.

? that's not what you said.

I think it's exactly what I said. I am distinguishing between the pay (amount of money) and the pay rate (amount of money per unit of time).
At a pay rate of $30/hour your total amount to be paid increases by $30 each hour. In terms of graphs, the pay rate is the slope of the graph of P = 30t, or 30. The total amount paid for t hours would be 30t dollars.

Think an increasing rate of pay would be when you get a raise, but I sort of see how you are looking at it.

In my example, the rate of pay is constant (30), but the amount paid is increasing.

 

[tech99]

I have always been worried about these things, but there is no easy answer.
Today we did a question asking for two advantages of a temp probe/data logger over a thermometer. Well it has better resolution, but the second answer was that there is less chance of error with a digital display. I would be hard pressed to have picked the answer they want out of several possibilities.

 

[phinds]

In my example, the rate of pay is constant (30), but the amount paid is increasing.

I think you must have responded while I was editing my post because I realized that. Thanks.

 

[Mark44]

For completeness, in case anyone's interested, here is the complete context of the "rate" question as originally sent to OCR:

A velocity/time graph shows an upward-curving line between t=0 & 2, and a straight descending line between 4=2 & 7. The question invites the student to describe the motion of the object.

Above, I assume you meant "straight descending line between t = 2 and 7"

On the interval [0, 2] is the graph concave up? If so, we have v > 0 and increasing, and acceleration > 0. On the interval [2, 7], we have v > 0 (I think, but don't have the graph to look at) and decreasing, but if the graph shows a straight line, the acceleration < 0. I.e., the object is decelerating.

That seems clear enough until you see the answer scheme. Two things puzzle me:

1. It FORBIDS any answers using "rate of acceleration". Please explain why. Later on (Q2a), you accept that same term. What is wrong with it?

Because acceleration already is a rate ($\frac {dv}{dt}$ or the second derivative of the position with respect to time). "Rate of acceleration" implies how the acceleration is changing with respect to t.

2. Part 2 FORBIDS "constant acceleration". Why? The term "deceleration" is accepted, but any constant deceleration is also a constant acceleration whose magnitude is negative; it's still an acceleration. If I toss a ball into the air and consider its vertical velocity, we can note that it will have an initial upwards velocity (which we can arbitrarily label "positive"). It will slow down, then stop, then change direction and velocity will increase in the negative direction. If we plot its vertical velocity over that time, we'll see those velocities move from positive, through zero, to negative. Throughout this period the acceleration is a constant - g. So it has sped up, stopped, changed direction and sped up again, but it's perfectly correct to say it's ACCELERATION was constant, and it would be odd to say its DECELERATION was anything.

Like I said earlier, it seems that the part 2 answer scheme wants the student to say simply whether the object is accelerating or decelerating. The simplest answer, without getting into the weeds with pos./neg. acceleration is that the object is accelerating for the first two seconds, and decelerating for the next five seconds. When humans write these questions and answers for automated-scoring tests, they don't always think of all the varied ways that other humans can respond.

 

[ChrisXenon]

Above, I assume you meant "straight descending line between t = 2 and 7"

On the interval [0, 2] is the graph concave up? If so, we have v > 0 and increasing, and acceleration > 0. On the interval [2, 7], we have v > 0 (I think, but don't have the graph to look at) and decreasing, but if the graph shows a straight line, the acceleration < 0. I.e., the object is decelerating.
Because acceleration already is a rate ($\frac {dv}{dt}$ or the second derivative of the position with respect to time). "Rate of acceleration" implies how the acceleration is changing with respect to t.

Like I said earlier, it seems that the part 2 answer scheme wants the student to say simply whether the object is accelerating or decelerating. The simplest answer, without getting into the weeds with pos./neg. acceleration is that the object is accelerating for the first two seconds, and decelerating for the next five seconds. When humans write these questions and answers for automated-scoring tests, they don't always think of all the varied ways that other humans can respond.

Mark, yes, apologies - the straight descending line is between t = 2 and 7.
And yes, concave up for 0 to 2. [The paper is here BTW]
As before, I now understand what you and the question setter meant - rate is measurement of how one thing changes with another. And you used my own example - rate of pay - to show me how. I agree and I have moved my view somewhat - but I continue to thik that "rate of acceleration" should not be clobbered - though I think "rate of change of acceleration" should be.

On to part 2. I don't think the simplest answer is necessarily the one you give, and whether or not it is the simplest answer hasno bearing on whether or not it is the only acceptable one.I agree that people are human - and I'm not out for a linching - I'm just trying to extablishcorrect and incorrect and go from there.

You have helped me to see that question setter's viewpoint on the "rate" argument, though I think it's marginal and the marking scheme is mean. I still think he is totally wrong on part 2.

Anyway, thank you for your time and your patience with me. Before I can form a confident view of OCR's performance I'll need to look at a few more examples and hopefully people here will be as generous as you ave been.

 

[ChrisXenon]

Justify means you need to explain how you got the answer. Many students may be able to tell you the resistance is effectively infinite below the threshold voltage, but if you were to ask them why it is so, they'll say, "I don't know," because all they did was memorize a result without understanding the reasoning behind it.

As to what level of justification is appropriate, that's a part of the art of test-taking. Frankly, given the question, I think your interpretation of explaining in terms of semiconductor behavior would be overkill, but you know the test better than I do.

Vela - thanks. "Justify" CAN mean "explain how you got the answer" but that is not the only possible meaning it can have. We could do an etymological analysis (Justify means "show or prove to be right or reasonable") but that doesn't really help us here. One can look at that and say "See - just what I said!" but there are still other valid interpretations.

If you feel this is wrong, I'd appreciate you explaining why it CANNOT mean "explain what is happening in the semiconductor".

Thing is - this could be easily fixed by clarifying the question to something like "by referring to the graph, justify your answer" or "explain your answer in terms of the data shown in the graph".

 

[ChrisXenon]

? that's not what you said.I think an increasing rate of pay would be when you get a raise, but I sort of see how you are looking at it. You are considering that the PAY is increasing, not that the RATE of pay is increasing.

I agree with you Phinds - whilst Mark's interpretation is strictly correct, I don't think it would be the common interpretation - that would be the pay raise interpretation. Of course, appeaking to "common interpretations" is dodgy ground in the physics world where common parlance is woefully inadequate, but I continue to think that the stipulation to punish "rate of acceleration" is wrong.

And in fact, if rate DOES mean that - then what on Earth does "rate of change" actually mean? Or is it tautological?

 

[ChrisXenon]

You are correct on both counts and I also agree with your analysis of the other problem you mentioned.

I've often found this kind of idiocy on "standardized" tests, which often seem to have been formulated by bureaucrats, not teachers.

I'm curious to know if you work in teaching Phinds, if you're willing to say.

 

[PeroK]

Regarding acceleration, I agree that acceleration could be negative, zero, or positive, but if the question specifically asks whether an object is accelerating or decelerating, and a < 0, then the correct answer would be "decelerating," IMO.

Technically, however, acceleration is a vector. There are no cases, IMO, where acceleration in a physics context is invalid and deceleration valid.

Also, deceleration is not where $a < 0$. Deceleration is where, in 1D motion, acceleration and velocity have opposite signs.

Or, more generally in 3D motion, where the magnitude of the velocity is decreasing.

For example.

A body falling under gravity is subject to a constant acceleration. There can be no argument about this. This is not an incorrect statement, whatever the OCR exam board thinks.

The idea that the only valid description is that the body decelerates on the way up and accelerates on the way down is not physics.

 

[phinds]

I'm curious to know if you work in teaching Phinds, if you're willing to say.

No, but my wife does and has shown me some tests, in addition to my own personal experience.

I have some experience in tutoring young people who are studying for their high school equivalency degree (used to be GED but is now called TASC in New York).

Just the other night I was looking at a new teaching manual that they are not yet required to use but are going to be required to use sometime soon and it is HORRIBLE. One of the first problems I looked at was a supposedly simple word problem at the 4th / 5th grade level and it was so confusing that I could not figure it out so I asked the lady there who had been teaching and tutoring math for 30 years and she could not figure it out either. The answer and discussion they gave for the question at the end of the section made no sense at all. She said the whole new set of books is almost that bad throughout. And this is just NY state. I hear others (not all of course) are just as bad or worse

 

[ChrisXenon]

No, but my wife does and has shown me some tests, in addition to my own personal experience.

I have some experience in tutoring young people who are studying for their high school equivalency degree (used to be GED but is now called TASC in New York).

Just the other night I was looking at a new teaching manual that they are not yet required to use but are going to be required to use sometime soon and it is HORRIBLE. One of the first problems I looked at was a supposedly simple word problem at the 4th / 5th grade level and it was so confusing that I could not figure it out so I asked the lady there who had been teaching and tutoring math for 30 years and she could not figure it out either. The answer and discussion they gave for the question at the end of the section made no sense at all. She said the whole new set of books is almost that bad throughout. And this is just NY state. I hear others (not all of course) are just as bad or worse

Thanks. That is very depressing. One wonders what kind of an organisation can oversee such stuff. One whic hshould be packed full of intelligent well-motivated professionals, and yet - one which clearly isn't.

 

[ChrisXenon]

Technically, however, acceleration is a vector. There are no cases, IMO, where acceleration in a physics context is invalid and deceleration valid.

Also, deceleration is not where $a < 0$. Deceleration is where, in 1D motion, acceleration and velocity have opposite signs.

Or, more generally in 3D motion, where the magnitude of the velocity is decreasing.

For example.

A body falling under gravity is subject to a constant acceleration. There can be no argument about this. This is not an incorrect statement, whatever the OCR exam board thinks.

The idea that the only valid description is that the body decelerates on the way up and accelerates on the way down is not physics.

Extremely well put.

 

[PeroK]

Extremely well put.

PS one further point is that the concept of deceleration is dependent on the reference frame. An aircraft taking off is accelerating relative to the surface of the Earth, but if it is traveling west it is decelerating in an inertial frame where the Earth is rotating west to east.

Again this shows the limited value of the whole concept of deceleration to physics. The acceleration is frame-invariant. Whereas the magnitude and direction of the velocity are not.

 

[ChrisXenon]

PS one further point is that the concept of deceleration is dependent on the reference frame. An aircraft taking off is accelerating relative to the surface of the Earth, but if it is traveling west it is decelerating in an inertial frame where the Earth is rotating west to east.

Again this shows the limited value of the whole concept of deceleration to physics. The acceleration is frame-invariant. Whereas the magnitude and direction of the velocity are not.

Agreed.

 

[anorlunda]

I can't think of any solution to this problem that I would not preface with HORRORS.

1 HORRORS no standardized tests. Every teacher invents his own standard.

2 HORRORS every standardized test grader decides for himself which answer is correct.

3 HORRORS the wordings of questions and answer choices is designed by committee.

4, 5, 6, ... there is no end to horrible choices.

Could it be that the underlying evil is the multiple choice question?

 

[atyy]

@ChrisXenon, I don't agree with all your points, but definitely quite a number of them. Just wondering - do you have problems with A-levels boards other than OCR? Are the marking schemes consistent across different A-level boards?

 

[pbuk]

Vela - thanks. "Justify" CAN mean "explain how you got the answer" but that is not the only possible meaning it can have. We could do an etymological analysis

We don't need to do an etymological analaysis, every exam board in the UK publishes their definition of these command verbs and OCR tells us that when they say "justify" they mean "present a reasoned case for actions or decisions made". I think it is likely that if the examiner was looking for something else, he would have said "explain" or "explain in terms of semiconductor behaviour" EDITED but as semiconductor behaviour isn't in the A level OCR syallbus, this shouldn't be a concern. You haven't given the full background to your 'rate of acceleration' issue (the question, the marking scheme and the examiner's report should all be available on line) so it is harder to see what is going on here.

Every board publishes syllabi and teaching materials geared to those syllabi. Now one can argue that this just gives them a license to print money, and this system is a terrible way to teach and examine scientific knowledge, however this is not going to help your pupils get a better exam grade. To do that you need to accept the fact that any system for teaching and examining hundreds of thousands of pupils a year is going to have imperfections and do your research on the exam board's specifications and requirements. You then need to pass on this knowledge to your pupils to pass the exam.

That doesn't mean that every marking scheme for every question is perfect of course, far from it, and where there is a clear problem you can be sure that many teachers whose pupils have sat those exams will have challenged them and asked for re-marks. But pick your battles - if you want to challenge an exam board about what they are expecting to see as an answer, first check what they have TOLD you about what they are expecting to see.

Note that these comments only apply to UK GCSE and A-level examinations, I have no knowledge of other systems. Note also that I am not suggesting that science teachers should only teach pupils to pass exams - they must also impart understanding of and enthusiasm for the subject, and I am sure the latter is what motivates most good teachers to teach. But to be a good teacher, you must also (however unwillingly) embrace the former.

 

[pbuk]

OCR Physics A H156/01 May 2016, Q27.
...
Both my student and I would have scored no points for that question.

I have looked at the mark scheme for that paper: assuming you described correctly the increasing and decreasing resistance, you would have scored at least 3 of the 4 marks available for that question. If the marker had time to read your explanation of semiconductor physics and liked it you might have got the 4th mark but as semiconductor theory is not in the OCR A level Physics syllabus it is unlikely.

 

[ChrisXenon]

pbuk - are you saying that markers are at liberty to award marks olutside of the marking scheme - for general awesomeness?

 

[ChrisXenon]

We don't need to do an etymological analaysis, every exam board in the UK publishes their definition of these command verbs and OCR tells us that when they say "justify" they mean "present a reasoned case for actions or decisions made". I think it is likely that if the examiner was looking for something else, he would have said "explain" or "explain in terms of semiconductor behaviour" EDITED but as semiconductor behaviour isn't in the A level OCR syallbus, this shouldn't be a concern. You haven't given the full background to your 'rate of acceleration' issue (the question, the marking scheme and the examiner's report should all be available on line) so it is harder to see what is going on here.

Every board publishes syllabi and teaching materials geared to those syllabi. Now one can argue that this just gives them a license to print money, and this system is a terrible way to teach and examine scientific knowledge, however this is not going to help your pupils get a better exam grade. To do that you need to accept the fact that any system for teaching and examining hundreds of thousands of pupils a year is going to have imperfections and do your research on the exam board's specifications and requirements. You then need to pass on this knowledge to your pupils to pass the exam.

That doesn't mean that every marking scheme for every question is perfect of course, far from it, and where there is a clear problem you can be sure that many teachers whose pupils have sat those exams will have challenged them and asked for re-marks. But pick your battles - if you want to challenge an exam board about what they are expecting to see as an answer, first check what they have TOLD you about what they are expecting to see.

Note that these comments only apply to UK GCSE and A-level examinations, I have no knowledge of other systems. Note also that I am not suggesting that science teachers should only teach pupils to pass exams - they must also impart understanding of and enthusiasm for the subject, and I am sure the latter is what motivates most good teachers to teach. But to be a good teacher, you must also (however unwillingly) embrace the former.

pbuk this reply is very helpful for me and goes some way to explaining how things may not be as bad as I feared.

Whilst I have degree level physics, I do not work in a school and I have taken an ad hoc approach to teaching A level physics. You have exposed a flaw in that appoach which I thank you for. I did not know there were board definitions for action verbs or any other part of Enligh language. I will need to obtain them an use them in my teaching, and I will have to be on my guard for defficiencies like this in the future.

HOWEVER I agree that this is a DREADFUL way to conduct education. My student clearly did not and does not have any knowledge of these special verb usages, and so I imagine, neither do his teachers. Whatever the intended outcome, the actual outcome is shambolic in a way which could fail him. My student, by the way, is attending a very expensive public school (which in the UK means one you pay to go to, outside of taxes).

Any system which finds the need to redefine the English language is, in my view, idiotic. What is wrong with using the existing language effectively? Why not say "justify by reference to the graph"? I can confidently say that there is a hell of a lot wrong with saying "Justify*" and then - in some place no student will ever see, have this:

* Note: Any and all words may not have their normal meaning. The OCR board reserve the right to re-define English to the utter bewilderment of humanity. No responsibility accepted. Your mileage may vary. My dad's a policeman.

The rated of acceleration question is here and the marking scheme is here

I note your point about basically accepting the system for what it is and leanring to succeed within it, and to a degree I accept it. As I mentioned, I DO need to get that verb list and apply it. However, a genetic fault I have is being unable to swallow a stinking status quo, which is why I have approached OCR (and have subsequently pointed them to this thread) and why I have no friends.

I want the board to fix their flaws; I think it's a better solution for the planet than the planet learning to accept the OCR's flaws, and if they don't want to play that game, then I'd quite like to wipe them off the face of the globe, because the current approach is arrogant, complacent, and highly damaging.

And I think being a good teacher might involve inspiring critical thinking in one's students and giving them the iron it takes to make a stand in the world.

But - big picture - you are cleary knowledgeable in both physics and the ways of the OCR and so you're a huge asset and I appreciate your time here.

UPDATED: You say [when they say "justify" they mean "present a reasoned case for actions or decisions made".] OK I've explained why I think it'a wrong to use words then offline their special meaning, but even if they had said "present a reasoned case for " instead of "justify" - it doesn't move us forward at all, does it? I still don't se ehow it can't mean "present a reasoned case in terms of semiconductor physics".

 

[ChrisXenon]

@ChrisXenon, I don't agree with all your points, but definitely quite a number of them. Just wondering - do you have problems with A-levels boards other than OCR? Are the marking schemes consistent across different A-level boards?

I only have one A level student and I would not have him but for historical circumstances, and he is with the OCR, so I don't know if I would have a problem with another board.

 

[ChrisXenon]

I can't think of any solution to this problem that I would not preface with HORRORS.

1 HORRORS no standardized tests. Every teacher invents his own standard.
2 HORRORS every standardized test grader decides for himself which answer is correct.
3 HORRORS the wordings of questions and answer choices is designed by committee.
4, 5, 6, ... there is no end to horrible choices.

Could it be that the underlying evil is the multiple choice question?

Sorry I don't understand your point.

 

[ChrisXenon]

This thread will shortly become unmanagable but here's the latest crank of the handle with OCR. My inline response to the question setter begin with >>

Thank you for your continued correspondence on mark schemes [...]

Note that the question is not about LEDs in general, but about a particular LED.

>> I understand but do not see the relevance of your distinction.

Candidates have been provided with a graph of the I-V characteristic of this LED and would be expected to
use it in their response. We are always careful to make sure that it is clear whether a question
refers to a specific object or a class of objects, as has been done here.

>> OK but again - I don't see the relevance here

The command “Describe and justify...” requires candidates to do two things for each potential
difference range. First they must describe the variation of resistance, and second they must
provide some evidence for that variation with the expectation that this comes from the
information given to them in the question, ie the graph.

>> You are describing your intended interpretation. I already knew it once I read your marking scheme.
But the significant fact is that I did not know it before - it was not evident from the question.
Someone on the physics forum has said OCR publishes a set of verbs and special meanings.
Is that true? Where would I find it? Honestly, I HATE that idea - it is all wrong. Use the existing language
effectively and unambiguously - don't redefine it in an appendix which no one will ever see then punish them for misunderstanding it!

The mark scheme and examiner’s report are clear that this sort of response is exactly what was given by candidates, and therefore that
the question was not found to be ambiguous.

>> If most students got it right, then I suppose most students gave the interpretation you intended.
But I am surprised if that is so, and it doesn't change the fact that the term "justify" could legitimately mean a multitude of things.
To satisfy me you'd need to explain why the questions CANNOT mean "explain this behaviour in terms of semiconductor physics".

The answer given in the main part of the scheme is generally a minimally acceptable answer,
with clarification in the guidance column. It is very likely that a more discursive response about
the general properties of semi-conductors would be awarded all four marks since it would
contain the necessary information. Since the given mark scheme would cover such a response,
there would not be any need to include any mention of it in the mark scheme.

>> You seem to be saying (I paraphrase with no intention to offend you):
"It is OK to ask an ambiguous question because in a lengthy written answer the candidate is likely to provide what is required inadvertently"
I assume I must have misunderstood you. Please clarify.

Regards
Chris

 

[anorlunda]

Sorry I don't understand your point.

My point is similar to what you said in a later post.

HOWEVER I agree that this is a DREADFUL way to conduct education. My student clearly did not and does not have any knowledge of these special verb usages, and so I imagine, neither do his teachers.

The language of physics is mathematics. This thread discusses an exam question posed verbally, with multiple choice answers given verbally. Then we run into problems because natural language is imprecise and subject to interpretation.

The solution would be the old fashioned type of exam where the student is required to derive his/her own equations and solve for the answer. The symbols used are the student's choice. We use math as much as possible in the question and the answer. It is the technical analog to "essay" type questions.

Of course that type of exam means many fewer questions are possible in the allotted time. It is also much more demanding and time consuming on the person doing the grading. It also introduces some grading subjectivity. (Should I allow 8 out of the max 10 points for this answer?) But it avoids exactly the dependency on word definitions you are complaining about.

I always thought that the drift towards multiple choice verbal exam questions, is motivated by the ease of machine grading. Multiple choice also allows more questions in the exam, e.g. 100 shallow questions instead of 10 in-depth questions.

 

[f95toli]

HOWEVER I agree that this is a DREADFUL way to conduct education. My student clearly did not and does not have any knowledge of these special verb usages, and so I imagine, neither do his teachers. Whatever the intended outcome, the actual outcome is shambolic in a way which could fail him. My student, by the way, is attending a very expensive public school (which in the UK means one you pay to go to, outside of taxes).

By now your student should have a pretty good idea of what is expected of him when answering a question; and that includes how to interpret the verbs.

It is important to note that when studying for an A level in a subject in the UK the students are NOT taking a "general" A-level course. Everything -including the syllabus- is set by a specific exam board. Hence, if the teacher has done his/her job right the students will from day one be asked questions of the same type, where the same language is used.

The way the system is set up it is certainly not about learning physics; it is about learning how to pass an exam from a specific exam board.

At my step-sons school they stopped teaching them new material back in November; for the past few months they have only been revising; it reality practicing how to answer questions in the exams (which start in June).

They also spent a couple of months preparing for the mocks in year 1. Hence, out of a two year course a little over half is spent on revising and preparing for the exams; NOT learning new material.

So yes, the system is broken (by design) but there isn't much you can do about it.

 

[ChrisXenon]

f95toli, my commments inline with yours:

By now your student should have a pretty good idea of what is expected of him when answering a question; and that includes how to interpret the verbs.

>> Well, by now I should be slimmer and more patient - but I ain't either. The reality is that he has had no training in the special use of English foisted upon us by OCR. And, as I've mentioned that arbitrary reality is also un-necessary and tiresome.

It is important to note that when studying for an A level in a subject in the UK the students are NOT taking a "general" A-level course. Everything -including the syllabus- is set by a specific exam board. Hence, if the teacher has done his/her job right the students will from day one be asked questions of the same type, where the same language is used.

>> Same commens as above. What should be and what is are not related here.

The way the system is set up it is certainly not about learning physics; it is about learning how to pass an exam from a specific exam board.

>> The two should be very closely allied or soemthing is very wrong. What's a physics A level FOR, for goodness sake? I suggest it should not be to prove someone can learn and apply some alternate Engloid language.
At my step-sons school they stopped teaching them new material back in November; for the past few months they have only been revising; it reality practicing how to answer questions in the exams (which start in June).
They also spent a couple of months preparing for the mocks in year 1. Hence, out of a two year course a little over half is spent on revising and preparing for the exams; NOT learning new material.

I don't see anything with revising or consolidating mateial or techniques. What I'm objectgivnig to is the use of ambiguous questions and non-standrard inter[retations of English.

So yes, the system is broken (by design) but there isn't much you can do about it.

>> I thinh there is a lot people can do when they try.

 

[pbuk]

I did not know there were board definitions for action verbs or any other part of Enligh language. I will need to obtain them an use them in my teaching, and I will have to be on my guard for defficiencies like this in the future.

Oops sorry, I meant to provide a link https://www.ocr.org.uk/Images/273311-command-verbs-definitions.pdf - but now I look again I see this is for OCR 'Cambridge Technicals' not A-levels so there may be some differences. There will be an equivalent somewhere on the OCR site - you will get access to more materials if you register as a teacher, and even more if you pay for the teachers' pack.

HOWEVER I agree that this is a DREADFUL way to conduct education. My student clearly did not and does not have any knowledge of these special verb usages, and so I imagine, neither do his teachers. Whatever the intended outcome, the actual outcome is shambolic in a way which could fail him. My student, by the way, is attending a very expensive public school (which in the UK means one you pay to go to, outside of taxes).

Fee-paying schools in the UK are usually very good at this aspect of getting students through exams, but almost all schools are having difficulty with recruitment for Physics in particular - this is and has been an increasing problem over the past decade.

Any system which finds the need to redefine the English language is, in my view, idiotic. What is wrong with using the existing language effectively? Why not say "justify by reference to the graph"? I can confidently say that there is a hell of a lot wrong with saying "Justify*" and then - in some place no student will ever see, have this:

* Note: Any and all words may not have their normal meaning. The OCR board reserve the right to re-define English to the utter bewilderment of humanity. No responsibility accepted. Your mileage may vary. My dad's a policeman.

I have to disagree with you there, I think that defining terms clearly enables the examiner to communicate what is required more effectively than would otherwise be the case. They are not out to trick you, and if they present you with a graph and and ask you to justify an answer then it is clear that they want you to justify your answer by reference to the graph.

The rated of acceleration question is here and the marking scheme is here

I see for 1(c)(i)2 either 'constant deceleration' or 'constant negative acceleration' is allowed so that is not at issue. However I agree that for 1(c)(i)1 'The object is accelerating at a constant rate' should be an acceptable answer, and the mark scheme implies that it is not. In situations like this, further insight can often be gained from the examiner's report (remembered to link it this time!). Here he says "The correct way to have used rate to score the mark would be to write 'increasing rate of change of velocity', which a few candidates did." Further insight into the examiner's point of view is in the comment to the first part of this question: "A noticeable incorrect answer was 'the rate of change of velocity per unit time';candidates need to be aware that in dynamics the term 'rate' includes per unit time." This examiner clearly has a bee in their bonnet about the use of the word 'rate', and like you I think he is taking it too far. However now you know this you know that you need to be careful when talking about rates in OCR A level Physics exams (assuming this situation persists - check more recent exams).

As someone mentioned further up the thread, top schools and crammers finish teaching the syllabus by the end of the autumn term (assuming a 2 year cycle - AS's are a very unwelcome distraction). The rest of the time before the exams is spent making sure through practice that students know how to read questions to find out what the examiner wants, and know how to turn their knowledge into an answer that gives it to him.

I still don't se ehow it can't mean "present a reasoned case in terms of semiconductor physics".

Because (i) there is a graph in front of you which you are expected to use and (ii) semiconductor physics is not part of the syllabus.

 

[Mark44]

Of course, appeaking to "common interpretations" is dodgy ground in the physics world where common parlance is woefully inadequate, but I continue to think that the stipulation to punish "rate of acceleration" is wrong.

Like you say, "common interpretations is dodgy ground in the physics world..." Acceleration is already a rate, so the phrase "rate of acceleration" muddies the waters, IMO. To me, "rate of acceleration" just seems sloppy.

And in fact, if rate DOES mean that - then what on Earth does "rate of change" actually mean? Or is it tautological?

"Rate of change," is more precisely phrased as "rate of change of one variable with respect to another." In terms of the OP, velocity is the time rate of change of position, and acceleration is the time rate of change of velocity. There is a physical term for the time rate of change of acceleration - jerk.
In more mathematical terms where position s is a function time, velocity $v = \frac{ds}{dt}$, and acceleration $a = \frac{dv}{dt} = \frac{d^2s}{dt^2}$, which I assume you already know. Before anyone jumps in, the equations represent motion in one dimension, so I'm ignoring the vector aspects.

 

[f95toli]

The two should be very closely allied or soemthing is very wrong. What's a physics A level FOR, for goodness sake?

I don't think there is a clear answer to this.

And no, I am not trying to be obtuse.

One of the things that frequently comes up when discussing the current system is that there are quite a few people (including members of government) who see A-levels, including the exams, as a way of "demonstrating potential". That is, the goal is not actually to learn the material but to show that you have the potential to learn once you are accepted to university. Hence, from this point of view A-level science is a bit like a game: the challenge is to win while -mostly- playing by the rules. However arbitrary.

This is the very same argument that is often used to justify why so many kids have to learn Latin in school: it is not about learning a language but about "training your brain".

I realize that none of this is -unfortunately- helping your current situation. But I think it is important to understand that your job as a tutor is NOT to teach your student physics but to help him pass the exam. The only way to do this is by learning the "rules" set by the exam board.
I think just about everyone in the academic community agrees that this is broken system; but this is ultimately a political question; there is nothing you as a tutor can do about it.

(some of my PhD students have made extra money by also tutoring A-level physics, so this is something that I've had many discussion about)

 

[sysprog]

I disagree, on etymological grounds, with the opposition to restriction of the use of the word 'acceleration' to non-negative values only. The prefix 'ac' means to; not from. The term 'acceleration' refers to increase in celerity. We have the prefix 'de' to allow denotation of decrease in celerity, i.e. 'deceleration'.

Similary, 'rate' being used consistently as non-negative allows us to use terms like 'rate of increase' and 'rate of decrease' without fear of ambiguity. It's cumbersome to call acceleration a 'negative rate of decrease in speed', even though it can be logically parsed.

The logics of the terms of natural language ideolects are not exclusively the province of scientists, and when there is no strong reason to depart from broader conventions, it is preferable that the experts of the various disciplines not feel compelled to alienate one another by non-standard usage.

 

[jedishrfu]

The underlying problem here is that everyday English is ambiguous and scientific usage is not or tries not to be so. These questions are often created by test developers not well versed in the subject who are likely adjusting an older version of the question to the current test to avoid repeated questions.

In some ways, it remind you of Family Feud where they ask for answers to some broad question and then compare your answers via "and the survey said..."

I know when I was in school, I would get confused by word problems especially percentage based ones confused in how to correctly apply the percentages or in computing them.

You'll probably need to create a lexicography of terms and what they most likely mean for this group of tests.

Also one needs to be careful not to over think the question. I know in my tutoring time, I would read more into a problem than what was present and get the student momentarily confused.

 

[ChrisXenon]

The underlying problem here is that everyday English is ambiguous and scientific usage is not or tries not to be so. These questions are often created by test developers not well versed in the subject who are likely adjusting an older version of the question to the current test to avoid repeated questions.

In some ways, it remind you of Family Feud where they ask for answers to some broad question and then compare your answers via "and the survey said..."

I know when I was in school, I would get confused by word problems especially percentage based ones confused in how to correctly apply the percentages or in computing them.

You'll probably need to create a lexicography of terms and what they most likely mean for this group of tests.

Also one needs to be careful not to over think the question. I know in my tutoring time, I would read more into a problem than what was present and get the student momentarily confused.

Thanks jedishrfu. I understand the concerns you raise, but for me the solution remains in linguistic precision - simply saying only and exactly what you mean.All other strategies ACCOMMODATE a problem - this one ELIMINATES the problem.

 

[sysprog]

Thanks jedishrfu. I understand the concerns you raise, but for me the solution remains in linguistic precision - simply saying only and exactly what you mean.All other strategies ACCOMMODATE a problem - this one ELIMINATES the problem.

I think that's often easier said than done, or not necessarily sufficient, e.g.:

officer to motorist: the speed limit here's 65; you were doing 85.​

motorist to officer: those two statements can't both be true.​

officer: you know exactly what I meant.​

motorist: I'm not clairvoyant. If I was doing 85, 65 can't really be the limit.​

o: ok, the legal speed limit is 65, you were doing 85, that means you violated the law.​

m: the sign didn't say legal speed limit, and neither did you at first.​

o: what did you think it meant?​

m: I thought it meant only and exactly what it said -- that nothing can go faster than 65 here.​

o: well then it would have said speed limit c instead of speed limit 65.​

m: there's no need for a local sign for a universal speed limit.​

o: ok, here's your ticket, you now know that those signs refer to legal speed limits.​

​

 

[pbuk]

@jedishrfu @sysprog @... - again, UK public exam boards now remove the majority of this uncertainty by publishing dictionaries of terms, syllabus requirements and even teaching materials. This may not be the case in other countries (and was not the case in the UK until ~20 years ago).

 

[f95toli]

The underlying problem here is that everyday English is ambiguous and scientific usage is not or tries not to be so. These questions are often created by test developers not well versed in the subject who are likely adjusting an older version of the question to the current test to avoid repeated questions.

That is -or at least should not- be the case here. The exam boards employ professional test developers who are at -least nominally- specialists in their subjects. They spend months developing each questions and the marking scheme (I actually know someone who does this for a living, albeit for math).
These are national tests here in the UK meaning any mistake (and they do happen...quite frequently) will literally end up in the national news.

Hence, things are -at least mostly- the way they are by design. That it is a bad design is a separate issue.

 

[jedishrfu]

I’ve not seen this happen often in the US. I’ve heard of students challenging the answers. In my time, one couldn’t even do that because nothing about the test was ever made public. Your best resource were test prep books where folks reverse engineered the problems at least that’s how we thought they got them.

 

[ChrisXenon]

I don't think there is a clear answer to this.

And no, I am not trying to be obtuse.

One of the things that frequently comes up when discussing the current system is that there are quite a few people (including members of government) who see A-levels, including the exams, as a way of "demonstrating potential". That is, the goal is not actually to learn the material but to show that you have the potential to learn once you are accepted to university. Hence, from this point of view A-level science is a bit like a game: the challenge is to win while -mostly- playing by the rules. However arbitrary.

This is the very same argument that is often used to justify why so many kids have to learn Latin in school: it is not about learning a language but about "training your brain".

I realize that none of this is -unfortunately- helping your current situation. But I think it is important to understand that your job as a tutor is NOT to teach your student physics but to help him pass the exam. The only way to do this is by learning the "rules" set by the exam board.
I think just about everyone in the academic community agrees that this is broken system; but this is ultimately a political question; there is nothing you as a tutor can do about it.

(some of my PhD students have made extra money by also tutoring A-level physics, so this is something that I've had many discussion about)

I agree that my personal and immediate goal is to return value ot my paying clients/students.
My hope is that

I think that's often easier said than done, or not necessarily sufficient, e.g.:

officer to motorist: the speed limit here's 65; you were doing 85.​

motorist to officer: those two statements can't both be true.​

officer: you know exactly what I meant.​

motorist: I'm not clairvoyant. If I was doing 85, 65 can't really be the limit.​

o: ok, the legal speed limit is 65, you were doing 85, that means you violated the law.​

m: the sign didn't say legal speed limit, and neither did you at first.​

o: what did you think it meant?​

m: I thought it meant only and exactly what it said -- that nothing can go faster than 65 here.​

o: well then it would have said speed limit c instead of speed limit 65.​

m: there's no need for a local sign for a universal speed limit.​

o: ok, here's your ticket, you now know that those signs refer to legal speed limits.​

​

Sysprog thanks for your input. Of course you're right but, it seems to me, not in a way that's relevant here. The issues before us are, fore example. the use of the word "justify" in the phrase "justify your answer". The dictionary definition of that word does not help us. The usage is ambiguous. The questions setter meant "by using the graph" and two of the readers (me and my student) thought he meant "in terms of semiconductor physics". The removal of that ambiguity is trivially eaasy. It should have been removed.

For me, that's the end of the story. Whilst it's true that language can and maybe has to be ambiguous sometimes, it doesn't have to be here, so I don't care.

 

[ChrisXenon]

I’ve not seen this happen often in the US. I’ve heard of students challenging the answers. In my time, one couldn’t even do that because nothing about the test was ever made public. Your best resource were test prep books where folks reverse engineered the problems at least that’s how we thought they got them.

I'm seeing this with another student, this itme doing City & Guilding level 2 English & Maths. My student keeps failing, and they consistently refuse to say how or where and I can't think of a good reason for that. The BAD reasons I can think of for that are (a) they can't be bothered and (b) they don't want to be accountable in case they're found incompetent.

 

[ChrisXenon]

That is -or at least should not- be the case here. The exam boards employ professional test developers who are at -least nominally- specialists in their subjects. They spend months developing each questions and the marking scheme (I actually know someone who does this for a living, albeit for math).
These are national tests here in the UK meaning any mistake (and they do happen...quite frequently) will literally end up in the national news.

Hence, things are -at least mostly- the way they are by design. That it is a bad design is a separate issue.

You say the test developers are "at least nominally [competent]". That's not good enough! They should be actually and demonstrably conspicuously competent, in my view.

Maybe things are the way they are through [bad] design and that may be a separate issue, but either way, it's an issue which is matters and seems tome to be entirely and easily avoidable.

 

[ChrisXenon]

@jedishrfu @sysprog @... - again, UK public exam boards now remove the majority of this uncertainty by publishing dictionaries of terms, syllabus requirements and even teaching materials. This may not be the case in other countries (and was not the case in the UK until ~20 years ago).

Can anyone explain why this isn't a better strategy?

1. Use the Oxford English Dictionary to find the meanings of words
2. Use language intelligently and unambiguiously.
3. Do not publish your own damned dictionary!

 

[Mark44]

Can anyone explain why this isn't a better strategy?

1. Use the Oxford English Dictionary to find the meanings of words
2. Use language intelligently and unambiguiously.
3. Do not publish your own damned dictionary!

The OED lists all definitions for a given word, so relying on it alone might not result in an unambiguous meaning.
A short list of key words and what they mean in the context of the exam can reduce ambiguity.