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I am involved in the teaching of an electric circuits course for engineering students. We get the students to build circuits and take various measurements using our test equipment. One of the major challenges is that we need to take measurements of rather small quantities, and our instruments aren't really suited to taking these measurements. What we see is that the number we get fluctuates, typically in the last 1-2 digits of a 4 digit display.

My major issue is that students tend to just take the first number they see, say it's "good enough", and write it down as "the" measurement. Is there an appropriate way to deal with measurements that are fluctuating? Is it just as simple as taking a bunch of measurements and taking the average?

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    $\begingroup$ My cheap Chinese blood pressure meter instructs me to always take the average of three measurements. In fact it's automatic mode does just that: runs the cycle three times, and shows the average at the end. $\endgroup$
    – Aksakal
    Commented Apr 9, 2018 at 20:16
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    $\begingroup$ I think this is an appropriate time to teach about significant figures. They should report as many digits as they are reliably able to measure consistently. $\endgroup$
    – AdamO
    Commented Apr 9, 2018 at 21:20
  • $\begingroup$ @AdamO sounds like a good idea indeed. For the most part, this will work well. However, there is one measurement we get them to take that is sort of designed to be terrible. The instrument doesn't settle at all in any of its digits. Is it appropriate to just say "the experimental procedures are not adequate to get a good measurement" and leave it in this type of situation? $\endgroup$
    – Michael Stachowsky
    Commented Apr 10, 2018 at 12:29
  • $\begingroup$ @MichaelStachowsky the procedures are accurate. The equipment is not. You design the equipment to fail? That's downright devious. I would say it's up to a judgement call on behalf of the student: if they get a crazy value, they can describe it and whether or not its consistent with their hypothesis, and point to the possibility that the equipment produced an error in their limitations. Or, the other way as you suggest: report a failure and comment on the need for better equipment to assess their hypothesis. $\endgroup$
    – AdamO
    Commented Apr 10, 2018 at 13:41

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