Are measured values and readings the same thing?

  • Thread starter Indranil
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In summary: Are measured values and readings the same thing in error in measurement?To me, they are the same thing. Can you tell us why you suspect that they might not be the same thing?
  • #1
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Homework Statement


Are measured values and readings the same thing in error in measurement?

Homework Equations


Are measured values and readings the same thing in error in measurement?

The Attempt at a Solution


Error = True value - measured value
 
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  • #2
If someone says: "the reading of voltmeter was 0.274 V", is that complete enough to count as a serious measurement? What if they say: "A voltage of 0.27##\pm##0.2 V was measured"?
 
  • #3
Indranil said:
Error = True value - measured value
This is meaningless.
Question: If you believe that the so called "true value" exists, how would you find out what it is?
Answer: You make a measurement.
Follow up: But the measurement always has an uncertainty built in it, so now what?
All you can provide with a measurement is a number and a bracket of uncertainty within which the value of the quantity that you are trying to determine most likely is. Think of it this way, the "true" value is by definition a number with zero uncertainty. How many significant figures might you need to express that number given the fact that it has zero uncertainty?
 
  • #4
Indranil said:
Are measured values and readings the same thing in error in measurement?
To me, they are the same thing. Can you tell us why you suspect that they might not be the same thing? For example, something you've read, e.g. conflicting statements in two sources?
 
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  • #5
I would rather be inclined to say that a reading of a measuring device doesn't, in the strictest sense, tell you anything unless you know something about the probability distribution of the errors in the readings. Suppose I create a bogus digital voltmeter that produces completely random numbers between 1.00 and 100.00 volts. You can certainly obtain a "reading" from that device, but you don't really do anything useful with it.
 
  • #6
kuruman said:
This is meaningless.
Question: If you believe that the so called "true value" exists, how would you find out what it is?
I don't see a problem here. Physics commonly assumes a true value exists, and it is quite reasonable to define the error in the measurement as measurement - true value (not the other way around). Stats theory does it all the time. It does not suppose you can ever determine the error value.
 
  • #7
hilbert2 said:
If someone says: "the reading of voltmeter was 0.274 V", is that complete enough to count as a serious measurement?
Yes.
hilbert2 said:
What if they say: "A voltage of 0.27±0.2 V was measured"?
I would say that the term "measurement" is widely used with both meanings. It can refer to an individual reading or to an estimate based on a set of readings.
I checked through several online academic resources and found they all use "measurement" in both senses in the same article. Generally they discriminate by calling a reading a single measurement.
 
  • #8
haruspex said:
I don't see a problem here. Physics commonly assumes a true value exists, and it is quite reasonable to define the error in the measurement as measurement - true value (not the other way around). Stats theory does it all the time. It does not suppose you can ever determine the error value.
If the purpose of the measurement is to find a value that is closest to the true value of the observable, then the equation makes more sense to me as true value = measurement ± error, where "error" is estimated independently of "measurement". With "error" on the left side of the equation, it can be construed as being a means of finding the error in the measurement. All is fine so far, unless one measures a quantity that has an "accepted value", e.g. the acceleration of gravity. In that case the "true value" is often replaced with the "accepted value" of 9.8 m/s2 by people who don't know any better. Thus the "error" does not express the confidence in one's measurement given its conditions, but becomes the discrepancy between one's measurement and somebody else's measurement. The distinction between uncertainty in a measurement and discrepancy between measurements is often missed by beginners.
 

1. Are measured values and readings interchangeable terms?

No, although they are closely related, measured values and readings are not necessarily the same thing. Measured values refer to the numerical data that is obtained through an experiment or observation, while readings typically refer to the actual numbers that are recorded during the experiment.

2. Can the terms measured values and readings be used in any scientific field?

Yes, the terms measured values and readings are commonly used in all areas of science. Whether it is in physics, chemistry, biology, or any other field, these terms are essential for accurately communicating experimental data.

3. Is there a difference between direct and indirect readings?

Yes, there is a difference between direct and indirect readings. Direct readings are obtained by reading a measuring instrument directly, while indirect readings are calculated using other measured values and mathematical formulas.

4. How do measured values and readings contribute to scientific research?

Measured values and readings are crucial in scientific research as they provide the data necessary to draw conclusions and make predictions. They also help to validate hypotheses and theories and can be used to make comparisons and identify patterns.

5. Can measured values and readings be influenced by external factors?

Yes, measured values and readings can be influenced by external factors such as environmental conditions, human error, and equipment limitations. This is why it is essential to carefully control and monitor these factors during experiments to ensure accurate results.

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