Question

A computer repair center advertises that it will solve any computer problem within 6 days. A sample of 46 past repairs is taken. The average repair time in the sample was 6.8 days with a standard deviation of 2.7 days. Assume that the repair time is normally distributed. Test to determine if their advertisement is legitimate at 5% significance level. (Show all steps)

Answer 1

a)

H0: <= 6

Ha: > 6

b)

Test Statistic :-
t = ( X̅ - µ ) / (S / √(n) )
t = ( 6.8 - 6 ) / ( 2.7 / √(46) )
t = 2.01
c)

Decisoin rule :-

Critical value t(α, n-1) = t(0.05 , 46-1) = 1.679
Reject null hypothesis if t > 1.679

d)

Decision = That is  2.01 > 1.679
Reject null hypothesis

Conclusion =

We have sufficient evidence to support the claim that mean repair time to solve any computer problem

is greater than 6 days.