# Question: A department store manager wants to estimate at a 98

A department store manager wants to estimate at a 98% confidence level the mean amount spent by all customers at this store. The manager knows that the standard deviation of amounts spent by all customers at this store is $31. What sample size should he choose so that the estimate is within $3 of the population mean?

**View Solution:**## Answer to relevant Questions

Refer to Exercise 8.24. A city planner wants to estimate, with a 97% confidence level, the average monthly residential water usage in the city. Based on earlier data, the population standard deviation of the monthly ...Briefly explain the meaning of the degrees of freedom for a t distribution. Give one example. Find the value of t from the t distribution table for each of the following. a. Confidence level = 99% and df = 13 b. Confidence level = 95% and n = 36 c. Confidence level = 90% and df = 16 a. A sample of 400 observations taken from a population produced a sample mean equal to 92.45 and a standard deviation equal to 12.20. Make a 98% confidence interval for ยต b. Another sample of 400 observations taken from ...Briefly explain how the width of a confidence interval decreases with a decrease in the confidence level. Give an example.Post your question