1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Significant figures in Results and Confidence Intervals

  1. May 19, 2012 #1
    Hello physicsforum people,

    I'm not sure how many significant figures I should express a confidence interval to. I have confidence intervals for means that I need to express in a lab report, which I am going to do in the something ± something fashion. (I have assumed a normal distribution of the deviations of each measurement about the true mean, although it is not the calculation of the confidence intervals I have a problem with)

    The resultant something ± something else confidence interval should be accurate to arbitrary precision shouldn't it? (neglecting the fact that you would have used a finite precision computer to calculate it)

    If I were to round the bit left of the ± sign, I would shift the interval and if I round the bit to the right, I would narrow/broaden the interval. I am figuring that when making 95% confidence intervals in general, if you leave them un-rounded they will have a probability of containing the true mean closer to 95%, which is what I want, correct?

    So why would someone round one, other than to the precision at which the computer can calculate it? I know the rationale behind rounding is to avoid false precision, but when you are explicitly stating precision, I do not believe this is a problem.

  2. jcsd
  3. Jun 16, 2012 #2
    come on people, surely this is an easy question to answer. Can I rephrase it in a better way?
  4. Jun 16, 2012 #3


    User Avatar
    Science Advisor

    No, it's not an "easy" question because it depends entirely upon what conventions you want to use. There simply is NO correct answer.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook