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Elementary Statistics a Step by Step Approach
Number of Jobs A sociologist found that in a random
sample of 50 retired men, the average number of jobs
they had during their lifetimes was $7.2 .$ The population
standard deviation is $2.1 .$
a. Find the best point estimate of the population
mean.
b. Find the $95 \%$ confidence interval of the mean number of jobs.
c. Find the $99 \%$ confidence interval of the mean number of jobs.
d. Which is smaller? Explain why.