Question

Karen wants to advertise how many chocolate chips are in each Big Chip cookie at her bakery. She
randomly selects a sample of 78 cookies and finds that the number of chocolate chips per cookie in the
sample has a mean of 7.1 and a standard deviation of 3.5. What is the 95% confidence interval for the
number of chocolate chips per cookie for Big Chip cookies?

Answer 1

Solution :

Given that,

t _/2,df = 1.991

Margin of error = E = t_/2,df * (s /n)

= 1.991 * (3.5 / 78)

Margin of error = E = 0.8

The 95% confidence interval estimate of the population mean is,

- E < < + E

7.1 - 0.8 < < 7.1 + 0.8

6.3 < < 7.9

(6.3 , 7.9)