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Average Value

  1. Sep 27, 2006 #1
    How do you find the average value in an experiment when all it consist of is weighing a beaker and adding 10 mL of water three times to it?
     
  2. jcsd
  3. Sep 27, 2006 #2

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    I am not clear on the procedure. Before each weighing, do you start with an empty beaker and then add 10 mL of water to it? Or do you add more water to the water from the previous weighing each time?
     
  4. Sep 27, 2006 #3
    Before the weighing we do weigh the beaker empty. Adding the 10mL comes afterwards but it happens three times, so it would be 10mL then 20mL then 30mL.
     
  5. Sep 27, 2006 #4

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    That is a very odd exercise. At first I thought it was to demonstrate the margin of human error that you might encounter when weighing the same amount of a substance during consecutive trials, but I am not sure what this is trying to teach.
    If you only want an average of the water weights I assume it is
    (total weight - beaker weight) for each of the three weighings, summed up and divided by total number of weighings (3), but I better back off here because there might be someone who is more familiar with this exercise.
    Did the teacher give any hints about what this would demonstrate?
     
  6. Sep 27, 2006 #5

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    You've got weights for three different 10ml additions do you not? How well can you measure 10 ml?
     
  7. Sep 27, 2006 #6
    Well I figured the average value would be the weight of the beaker empty. Since that is the original state it is in. I don't think that I have to consentrate on the 10mL part and I probably shouldn't have mentioned it. I know this is vague but if the average value isn't given then where else could it come from except for any original state.
     
  8. Sep 27, 2006 #7

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    ok, do you know how to compute an average (a mean?)
     
  9. Sep 27, 2006 #8
    Yes but isn't this more then just finding the mean?
     
  10. Sep 27, 2006 #9

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    Typically, when people ask for an average value they intend the mean value. (There are also averages of median and mode which are not applicable here.)
     
  11. Sep 27, 2006 #10
    Actually there is also a part that is called deviations from average which I found. The rest of the results are from weighing an empty beaker then adding 10mL of water three times, then we had to find the density of the water and the average density. After that was the deviations from the average.
     
  12. Sep 27, 2006 #11

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    yes, you can also compute a "standard deviation" from your weighings. Now is this a chemistry class or a statistics class?
     
  13. Sep 27, 2006 #12
    Chemistry. And I get exactly what you mean so thanks :biggrin:
     
  14. Sep 27, 2006 #13

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    yeah, I can see what you are saying. If you want to get a really good critique (if you have the time and inclination), you could post each question in the assignment, exactly as worded, followed by your answers and explanations of how you came to the conclusions. Then the experts here could go through them one by one.
    Chem teachers are quirky. I had one that I bailed on after two classes, and then another who was fantastic and made everything crystal clear.
     
  15. Sep 27, 2006 #14
    I probably should have bailed on this guy. He doesn't even know the english language that well -_-
     
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