an engineer has designed a valve that will regulate water pressure on an automobile engine. the valve was tested on 200 engines and the mean pressure was 4.4 lbs/square inch. assume the variance is known to be 0.81. if the valve was designed to produce a mean pressure of 4.5 lbs/square inch, is there sufficient evidence at the 0.05 level that the valve performs below the specifications? state the null and alternative hypotheses for the above scenario.
