Question

A chocolate chip cookie manufacturing company recorded the number of chocolate chips in a sample of 60 cookies. The mean is 22.36 and the standard deviation is2.97 . Construct a ​80% confidence interval estimate of the standard deviation of the numbers of chocolate chips in all such cookies.

Answer 1

2.665 < σ < 3.379

Explanation:

Given :

s = 2.97

Sample size, n = 60

α = 80%

χ² Critical value (two - tailed), df = (60-1) = 59

χ² = 45.577 ; χ² = 73.279

The 80% confidence interval for the standard deviation :

s * √(n - 1) / χ² critical

2.97 * √(60 - 1) / 73.279 < σ < 2.97 * √(60 - 1) / 45.577

2.665 < σ < 3.379