Question

1. M&M Cookies - Suppose you make a batch of Monster cookies with M&Ms in them and in the batch of 51, you find the mean number of M&Ms in the cookies to be 18.56 and the standard deviation to be 2.35. Construct a 95% confidence interval estimate of the standard deviation of the number of M&Ms in the cookies.
   1. In the problem above what population parameter are you being asked about?
      1. Proportion
      2. Mean
      3. Standard Deviation/Variance
      4. None of the above
   2. What distribution should you use to get your critical value?
      1. Standard Normal Distribution
      2. Student t Distribution
      3. Chi-square Distribution
      4. None of the above
   3. Construct the 95% confidence interval estimate of the standard deviation of the number of M&Ms in the cookies.

Answer 1

a)

Population parameter asked = Standard deviation

b)

Distribution we need to use = Chi square distribution,

c)

critical values at 0.05 significance level with 50 df = 32.357 , 71.420

95% confidence interval for is

Sqrt [ ( n - 1) S2 / U ] < < Sqrt [ ( n - 1) S2 / L]

sqrt [ (51-1) * 2.352 / 71.420 ] < < sqrt [ (51-1) * 2.352 / 32.357]

1.97 < < 2.92

95% CI Is ( 1.97 , 2.92 )