Question

The mean life of a television set is 97 months with variance of 169

If a sample of 59 televisions is randomly selcted what is the probablity that the sample mean would be less than 100.9 months?  round your answer to four decimal places

Answer 1

Solution :

mean = = 97

variance =  ² = 169

standard deviation = =  ² = 169 = 13

n = 59

=   = 97

= / n = 13/ 59 = 1.692

P( > 100.9) = 1 - P( < 100.9)

= 1 - P[( - ) / < (100.9 - 97) / 1.692]

= 1 - P(z < 2.30)

Using z table,    

= 1 - 0.9893

= 0.0107