Test Hypotheses About a Population Mean with Known Using Confidence $\mu = 639$

Short Answer

Test Hypotheses about a Population Mean with Known Using Confidence Intervals
-A random sample of 56 lithium batteries has a mean life of 645 hours with a standard deviation of 31 hours. A leading consumer journal states that the mean life for these batteries is $\mu = 639$ hours. Test this hypothesis by constructing a $95 \%$ confidence interval for the population mean.