1. Not finding help here? Sign up for a free 30min 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!

Probability of a Confidence Interval

  1. Jul 31, 2008 #1
    What's the probability that a confidence interval (with alpha=10%), will have at least 85 of 100 predicted means within the calculated interval range (xbar +/- 1.645(sigma/sqrt(n)))?

    I understand that on average 90% of my means will be located in this range (and I know how to find this range), but the figure 90% is an AVERAGE.

    Suppose I do this experiment ONCE, and only once. What's the probability that at least (>=) 85 (of the 100, or 85%) of the mean values will be within this range?

    Assumptions: Normal (by Central Limit Theorem as n=100 is greater than 30)

  2. jcsd
  3. Jul 31, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    sum(n=85,100,.9^n*.1^(100-n)*binomial(100,n)) ≈ 96% of the time.
  4. Jul 31, 2008 #3
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Probability of a Confidence Interval
  1. Confidence Intervals (Replies: 1)

  2. Confidence Interval (Replies: 1)

  3. Confidence Intervals (Replies: 0)

  4. Confidence intervals (Replies: 3)

  5. Confidence Interval (Replies: 4)