A sample of 100 widgets from the Acme production line shows that the average lifespan of these parts is 900 hours. The standard deviation of production has been 200 hours historically and is known to be normally distributed.
a) Give a point estimate of lifespan of all production.
b) Form an interval estimate for the students using a 99% confidence interval
c) Interpret the results you obtained in question }p
d) Assuming the sigma of 200 was actually the standard deviation for the sample, recalculate the interval estimate. Discuss how this changed your result from that in part b.