Question

In a study of the accuracy of fast food​ drive-through orders, Restaurant A had 268 accurate orders and 65 that were not accurate.

a. Construct a 95 ​% confidence interval estimate of the percentage of orders that are not accurate.

A)   _____ < p < _____

Answer 1

Sample proportion = 65 / (65 + 268) = 65 / 333 = 0.195

95% confidence interval for p is

- Z * sqrt ( ( 1 - ) / n) < p < + Z * sqrt ( ( 1 - ) / n)

0.195 - 1.96 * sqrt ( 0.195 * 0.805 / 333) < p < 0.195 + 1.96 * sqrt ( 0.195 * 0.805 / 333)

0.152 < p < 0.238