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 6.0 pounds/square inch. it is believed that the valve performs above the specifications. the valve was tested on 240 engines and the mean pressure was 6.1 pounds/square inch. assume the standard deviation is known to be 0.8 a level of significance of 0.05 will be used. determine the decision rule. Enter the decision rule.

Answer 1

This is the right tailed test .

The null and alternative hypothesis is

H₀ : = 6

H_a : > 6

Test statistic = z

= ( - ) /    / n

= (6.1 - 6) / 0.8 / 240

= 1.94

Test statistic = 1.94

= 0.05

z > 1.645

Critical value = 1.645

Test statistics > critical value

Reject the null hypothesis .