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 4.2 pounds/square inch. The valve was tested on 150 engines and the mean pressure was 4.3 pounds/square inch. Assume the standard deviation is known to be 0.8. Is there evidence at the 0.05 level that the valve performs above the specifications?

Step 1 of 5: Enter the hypotheses:

Step 2 of 5: Enter the value of the z test statistic. Round your answer to two decimal places.

Step 3 of 5: Specify if the test is one-tailed or two-tailed.

Step 4 of 5: Enter the decision rule.

Step 5 of 5: Enter the conclusion.

Answer 1

The statistical software output for this problem is:

Hence,

Step - 1: Hypotheses:

H₀ : μ < 4.2
H_A : μ > 4.2

Step - 2: z test statistic = 1.53

Step - 3: One - tailed

Step - 4: Decision Rule:

Reject Ho if z > 1.645

Step - 5: Do not reject the null hypothesis