Question

An engineer has designed a valve that will regulate water pressure on an automobile engine. The valve was tested on 180 engines and the mean pressure was 6.2 pounds/square inch (psi). Assume the population standard deviation is 0.8. The engineer designed the valve such that it would produce a mean pressure of 6.3 psi. It is believed that the valve does not perform to the specifications. A level of significance of 0.01 will be used. Find the value of the test statistic. Round your answer to two decimal places.

Answer 1

H0: = 6.3

Ha: 6.3

Test statistic

z = - / / sqrt(n)

= 6.2 - 6.3 / 0.8 / sqrt(180)

= -1.68

This is test statistics value.

Critical value at 0.01 level = -2.576, 2.576

Since test statistics falls in non-rejection region, we fail to reject the null hypothesis.