In Example 6, how many employees must the researcher include in the sample to be 95% confident that the sample mean is within 2 hours of the population mean? Compare your answer with Example 6.

a. Identify z_c, E, and σ.

b. Use z_c, E, and σ to find the minimum sample size n.

c. Interpret the results and compare them with Example 6.

Example 6

The economics researcher in Example 1 wants to estimate the mean number of hours worked by all grocery store employees in the county. How many employees must be included in the sample to be 95% confident that the sample mean is within 1.5 hours of the population mean?