A manufacturer claims that the mean

lifetime of its drill is 1000 hours. A

homeowner selects 25 drills and finds

the mean lifetime to be 980 hours with a

sample standard deviation of 80 hours.

If = 0.05, test the manufacturer's claim.

A manufacturer claims that the mean

lifetime of its drill is 1000 hours. A

homeowner selects 25 drills and finds

the mean lifetime to be 980 hours with a

sample standard deviation of 80 hours.

If = 0.05, test the manufacturer's claim.