A Simple Random Sample of Kitchen Toasters Is to Be $\sigma = 21$

question 45

Multiple Choice

A simple random sample of kitchen toasters is to be taken to determine the mean operational lifetime in hours. Assume that the lifetimes are normally distributed with population standard Deviation $\sigma = 21$ hours.
Find the sample size needed so that a 98% confidence interval for the mean lifetime will have a margin Of error of 4.

• A) 13
• B) 150
• C) 3
• D) 257