Question

A tire manufacturer claims its tires will last for 80,000 miles on average when properly maintained. To investigate this claim, a retail tire store has surveyed 49 recent customers of that particular tire and determined those tires lasted for an average of 77,470 miles. The population standard deviation is known to be 7,700 miles. Compute the value of the appropriate test statistic to test this claim.

Enter your answer as a decimal rounded to two places. Indicate a negative value with a "–" sign directly before the value.

Test statistic =

Answer 1

Solution :

The null and alternative hypothesis is ,

H0 :   = 80000

Ha :    80000

= 77470

= 7700

n = 49

Test statistic = z =

= ( - ) / / n

= (77470 - 80000) / 7700 / 49

Test statistic = z = -2.30