Question

Isabella wants to advertise how many chocolate chips are in each Big Chip cookie at her bakery. She randomly selects a sample of 26 cookies and finds that the number of chocolate chips per cookie in the sample has a mean of 63. Assume the population standard deviation is 3.3. What is the 99% confidence interval for the number of chocolate chips per cookie for Big Chip cookies? Assume the data is from a normally distributed population. Round answers to 2 decimal places where possible.

Answer 1

n = 26

= 63

= 3.3

SE = /

= 3.3/

= 0.6472

=0.01

From Table, critical values of Z = 2.576

Confidence Interval:

63 (2.576 X 0.6472)

= 63 1.6671

= ( 61.33 ,64.67)

The 99% confidence interval for the number of chocolate chips per cookie for Big Chip cookies :

61.33 < < 64.67