A light bulb manufacturer claims that, on average, their light bulbs burn for 3000 hours with a standard deviation of 1000 hours. You are the maintenance manager for Turner Field and you installed 400 of these light bulbs in one of the light standards at the ballpark. Assume the manufacturer’s claim is correct.

a) What is the probability that the average life time for these bulbs is greater than 3075 hours?

b) What is the probability that the average life time for these bulbs is between 2960 hours and 3095 hours?

c) You tracked the life times of all of the bulbs that you installed and determined that the mean life time for these bulbs was 2900 hours. What, if anything, does this tell you about the manufacturer’s claim?

Answer rating: 100% (QA)

a We first get the z score for the critical value As z x u sqrtn s then as x critical value 3075 u m... View the full answer