Question

An automobile manufacturer has given its jeep a 25.3 miles/gallon (MPG) rating. An independent testing firm has been contracted to test the actual MPG for this jeep since it is believed that the jeep has an incorrect manufacturer's MPG rating. After testing 190 jeeps, they found a mean MPG of 25.1. Assume the population standard deviation is known to be 2.4. A level of significance of 0.02 will be used. Make the decision to reject or fail to reject the null hypothesis.

Answer 1

This is the two tailed test .

The null and alternative hypothesis is

H₀ : = 25.3

H_a : 25.3

Test statistic = z

= ( - ) /    / n

= (25.1 - 25.3) / 2.4 / 190

Test statistic = -1.15

P-value = 0.2502

P-value > = 0.02

Fail to reject the null hypothesis