A manufacturer of personal computers tests competing brands and finds that the amount of energy they require is normally distributed with a mean of 285 kwh and a standard deviation of 9.1 kwh. If the lowest 25 percent and the highest 30 percent are not included in a second round of tests, what are the upper and lower limits for the energy amounts of the remaining computers?
A) [269.76, 300.24]
B) [278.86, 289.78]
C) [280.22, 289.78]
D) [280.22, 300.24]

Question

Quizplus · Accepted Answer

z_.25 = −.675 = (x − 285)/9.1 = 278.86 z_.70 = .525 = (x − 285)/9.1 = 289.78

A Manufacturer of Personal Computers Tests Competing Brands and Finds