Question

A light bulb manufacturer wants to determine how large a sample is needed to test the hours a light bulb has. The manufacturer wants to be 99% confident and a margin of error of 25 hours. It is known that the population standard deviation is 300 hours. What is the minimum number of light bulbs to be tested?

Answer 1

Solution :

Given that,

standard deviation =s =   =300

Margin of error = E = 25

At 99% confidence level the z is,

= 1 - 99%

= 1 - 0.99 = 0.01

/2 = 0.005

Z/2 = 2.576

sample size = n = [Z/2* / E] 2

n = ( 2.576* 300/ 25)2

n =955.55

Sample size = n =956 rounded