Records on a fleet of trucks reveal that the average life of a set of spark plugs is normally distributed with a mean of 22,100 miles.A manufacturer of spark plugs claims that its plugs have an average life in excess of 22,100 miles.The fleet owner purchased 18 sets and found that the sample average life was 23,400 miles,the sample standard deviation was 1,500 miles and the computed t = 3.677.Based on these findings,there is enough evidence to accept the manufacturer's claim at the 0.05 level.

Question

Quizplus · Accepted Answer

Since the computed t-value of 3.677 is greater than the critical t-value at the 0.05 level of significance with 17 degrees of freedom, the null hypothesis can be rejected. Therefore, there is enough evidence to accept the manufacturer's claim that their spark plugs have an average life in excess of 22,100 miles.

Records on a Fleet of Trucks Reveal That the Average