Question

the number of hours an American adult watches tv follows a normal distribution with an average of 6.9 hours a day with a standard deviation of .68 hours. If we take a random sample of 13 American adults what is the probability they have a sample mean less than 7.5 hours per day?

Answer 1

Solution :

Given that,

mean = = 6.9

standard deviation = = 0.68

n = 13

= 6.9

=  / n = 0.68 / 13=0.1886

P( < 7.5) = P[( - ) / < (7.5-6.9) /0.1886 ]

= P(z < 3.18)

Using z table

probability= 0.9993