Question

A survey of 20 randomly selected adult men showed that the mean time they spend per week watching sports on television is 9.34 hours with a standard deviation of 1.34 hours.

Assuming that the time spent per week watching sports on television by all adult men is (approximately) normally distributed, construct a 90 % confidence interval for the population mean,   μ .

Round your answers to two decimal places.

Lower bound: Enter your answer; confidence interval, lower bound

Upper bound: Enter your answer; confidence interval, upper bound

Answer 1

Solution :

degrees of freedom = n - 1 = 20 - 1 = 19

t/2,df = t_0.05,19 = 1.729

Margin of error = E = t_/2,df * (s /n)

= 1.729 * ( 1.34 / 20)

Margin of error = E = 0.52

The 90% confidence interval estimate of the population mean is,

  ± E  

= 9.34  ± 0.52

= ( 8.82, 9.86 )

lower bound = 8.82

upper bound = 9.86