Question 986136
Ho=mean is 375
Ha=mean is not 375
alpha=0.05
Test statistic is z=(xbar-mean)/100/(sqrt(64))
critical value is |z|>1.96
calculation is z=25*8/100=+2
Reject Ho.  There is a significant difference in the mean life of the population of light bulbs.
CI is 1.96*12.5=24.5 on each side, so it is (350.5,399.5).  The value of the sample mean is not in the confidence interval.
the p-value is 0.0456.  This means that if the true mean were 375, in a sample of 64, we would expect to get this result about 4.56% of the time, below the 5% cut-off we established at the outset.