Question

An engineer designed a valve that will regulate water pressure on an automobile engine. The engineer designed the valve such that it would produce a mean pressure of 7.6 pounds/square inch. It is believed that the valve performs above the specifications. The valve was tested on 140 engines and the mean pressure was 7.8 pounds/square inch. Assume the standard deviation is known to be 1.0. A level of significance of 0.05 will be used. Find the value of the test statistic. Round your answer to 2 decimal places. Enter the value of the test statistic.

Answer 1

The Hypotheses are:

Rejection region :

Reject Ho if Z > Z_0.05 =1.65, calculated from Z table shown below

Test statistic:

P-value:

P-value computed using Z table shown below as:

P-value= 0.0091

Conclusion:

Since P-value< 0.05 hence we reject the null hypothesis and conclude that there is enough evidence to support the claim.