Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

i forgot how to calculate 95% confidence interval?

there are 500 number of samples. 38 are defective. so the question is, 95% CI for this proportion defective is?

the answer is (0.053, 0.099) but i really want to know how to get there..

I've worked out the standard error for this, and it is 0.012 as sqrt*(pq/n), where p=(38/500)=0.076, q=1-0.076 =0.924

many thanks!

1 Answer

Relevance
  • 9 years ago
    Favorite Answer

    n = 500

    x = 38

    p = 38/500

    p = 0.076, q = 0.924

    sqrt((1/500)*(0.076*.924)) = 0.0118510759

    P(0.076 - 1.96*0.0118510759 < π < 0.076 + 1.96*0.0118510759) = 0.95

    P(0.05277 < π < 0.09923) = 0.95, answer!

    Source(s): Standardized Normal Distribution.
Still have questions? Get your answers by asking now.