Question

PLEASE TYPE

A trucking firm suspects that the mean life of a certain tire it uses is less than 35,000 miles. To check the claim, the firm randomly selects and tests 18 of these tires and gets a mean lifetime of 34,350 miles with standard deviation of 1200 miles. At α = 0.05, test the trucking firm’s claim.

Answer 1

Solution :

This is the two tailed test .

The null and alternative hypothesis is ,

H₀ :   = 35000

H_a : < 35000

Test statistic = z

= ( - ) / / n

= (34350 - 35000) / 1200 / 18

Test statistic = -2.30

P(z < -2.30) = 0.0172

P-value = 0.0172

= 0.05

P-value <

Reject the null hypothesis .

There is sufficient evidence to conclude that the mean life of a certain tire it uses is less than 35,000 miles .