Question

The mean life of a television set is 109 months with a variance of 324 If a sample of 77 televisions is randomly selected, what is the probability that the sample mean would be less than 110.2 months? Round your answer to four decimal places.

Answer 1

Solution :

Given that,

mean = = 109

Variance = ² = 324

standard deviation = = 18

n = 77

= 109

  =  ( /n) = (18 / 77 ) = 2.0513

A ) P( < 110.2 )

P ( -   / ) < ( 110.2 - 109 / 2.0513 )

P ( z < 1.2 / 2.0513 )

P ( z < 0.58)

Using z table

= 0.7190

Probability = 0.7190