In an examination of purchasing patterns of shoppers, a sample of 20 shoppers revealed that they spent, on average, $54 per hour of shopping. Based on previous years, the population standard deviation is thought to be $21 per hour of shopping. Assuming that the amount spent per hour of shopping is normally distributed, find a 90% confidence interval for the mean amount.

Question

Cristina Morales

Business

16 November, 20:00

In an examination of purchasing patterns of shoppers, a sample of 20 shoppers revealed that they spent, on average, $54 per hour of shopping. Based on previous years, the population standard deviation is thought to be $21 per hour of shopping. Assuming that the amount spent per hour of shopping is normally distributed, find a 90% confidence interval for the mean amount.

+3

Answers (1)

Know the Answer?

Aydan Walters · Answer 1

Confidence interval for the mean amount = 54+1.645*21/sqrt (16) = (62.64, 45.36)

Explanation:

confidence interval = mean + z*, where z * is the upper (1-C) / 2 critical value for the standard normal distribution.

z score for 90% confidence interval = 1.645

confidence interval for the mean amount = 54+1.645*21/sqrt (16) = (62.64, 45.36)