Records on a fleet of trucks reveal that the average life of a set of spark plugs is normally distributed with a mean of 35,600 kilometres. A manufacturer of spark plugs claims that its plugs have an average life in excess of 35,600 kilometres. The fleet owner purchased 18 sets and found that the sample average life was 37,700 kilometres, the sample standard deviation was 2415 kilometres and the computed t = 3.677.
A) Based on these findings, there is enough evidence to accept the manufacturer's claim at the 0.05 level.
B) Based on these findings, there is NOT enough evidence to accept the manufacturer's claim at the 0.05 level.
C) Based on these findings, there is enough evidence to accept the manufacturer's claim at the 0.05 level, but NOT at the 0.01 level.
D) Based on these findings, there is NOT enough evidence to accept the manufacturer's claim at the 0.01 level.
E) Based on these findings, there in NOT enough evidence to accept the manufacturer's claim at either the 0.05 or the 0.01 level.

Question

Quizplus · Accepted Answer

The computed t-value of 3.677 indicates that the sample mean of 37,700 kilometres is significantly higher than the population mean of 35,600 kilometres at the 0.05 level, supporting the manufacturer's claim of an average life in excess of 35,600 kilometres.

Records on a Fleet of Trucks Reveal That the Average