Question

4 pts

Suppose that an automobile manufacturer advertises that its new hybrid car has a mean gas mileage of 50 miles per gallon. You take a simple random sample of 30 hybrid-vehicles and test their gas mileage. You find that in this sample, the average is  47 miles per gallon with a standard deviation of s= 5.5 miles per gallon. Does this indicate that the advertiser’s statement is true or false , with a 0.05 level of significance?

What is the P-value ?

Answer 1

Solution :

= 50

=47

S =5.5

n = 30

This is the two tailed test .

The null and alternative hypothesis is ,

H0 :    = 50

Ha :     50

Test statistic = t

= ( - ) / S / n

= (47-50) / 5.5 / 30

= −2.988

Test statistic = t =  −2.988

P-value =0.0057

= 0.05  

P-value <

0.0057 < 0.05

Reject the null hypothesis .

There is sufficient evidence to suggest that