An engineer has 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 5.5 pounds/square inch. The valve was tested on 18 engines and the mean pressure was 5.4 pounds/square inch with a variance of 0.64. Is there evidence at the 0.1 level that the valve performs below the specifications? Assume the population distribution is approximately normal.