Problem
Question 4 of 20 , Step 1 of 1 Correct An engineer has designed a valve that will regulate water pressure on an automobile engine. The valve was tested on 160 engines and the mean pressure was 4 Ibs/square inch. Assume the standard deviation is known to be 0.9 . If the valve was designed to produce a mean pressure of $4.2 \mathrm{lbs} / \mathrm{square}$ inch, is there sufficient evidence at the 0.02 level that the valve performs below the specifications? State the null and alternative hypotheses for the above scenario. Answer Tables Keyboard Shor
Solution
Step 1 ：The null hypothesis, denoted as $H_0$, is: The mean pressure of the valve is 4.2 lbs/square inch.
Step 2 ：The alternative hypothesis, denoted as $H_a$, is: The mean pressure of the valve is less than 4.2 lbs/square inch.
