Bright Bulb light bulb company is planning a study to assess

Bright Bulb light bulb company is planning a study to assess the average life expectancy of their light bulbs. They know the standard deviation is hours. They want a 95% confidence interval with a margin of error of 50 hours.

Solution

Given a=0.05, Z(0.025) = 1.96 (from standard normal table)

So n=(Z*s/E)^2

=(1.96*400/50)^2

=245.8624

Take n=246