An engineer at a battery factory believes that she has improved the life span of batteries at her company. To test this,
she randomly selects 8 flashlights and puts in the traditional battery, turns on the flashlight, and keeps time of how long
(in hours) until the batteries die. She repeats this process with her new battery design. Finally, she takes the difference
of life span times: new - traditional.
The 8 differences are
28, 8, 2, 11, 4, 12, 19, -6.
(a)Find the point estimate (in hours),
for the mean difference in life spans.
(b)Assume that the distribution of the population is approximately normal. Find the critical value that would be used toestimate the population mean difference with 90% confidence. (Use a table or technology. Round your answer to three
decimal places.)
(9)Calculate the margin of error (in hours) of the point estimate for the population mean difference. (Use a table or
technology. Round your answer to three decimal places.)