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# A Simple Random Sample of Kitchen Toasters Is to Be $\sigma = 28 \text { hours. }$

Question 20
Multiple Choice
Question 20
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 $\sigma = 28 \text { hours. }$Find the sample size needed so that a 95 % confidence interval for the mean lifetime will have a margin of error of 4 .

A) 2
B) 385
C) 189
D) 14

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