Question

light bulbs. They took a sample of their light bulbs and measured the length of time that the light bulbs stayed lit. They sampled 100 light bulbs, and the average life span of bulbs was 700 hours. The population standard deviation of the life span is designed to be 50 hours.

What is the confidence interval of the population average life span of bulbs? Use α=0.05.

Answer 1

Solution :

Given that,

Sample size = n = 100

Z/2 = Z0.025 = 1.96

Margin of error = E = Z/2* ( /n)

= 1.96 * ( 50/ 100)

Margin of error = E = 9.8

At 95%confidence interval estimate of the population mean is,

- E < < + E

700 - 9.8 < < 700 + 9.8

690.2 < < 709.8

(690.2 ,709.8)

The confidence interval of the population average life span of bulbs is (690.2 ,709.8)