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 5.9 pounds/square inch. It is believed that the valve performs above the specifications. The valve was tested on 26 engines and the mean pressure was 6.2 pounds/square inch with a standard deviation of 0.9. A level of significance of 0.025 will be used. Assume the population distribution is approximately normal. Make the decision to reject or fail to reject the null hypothesis.

Answer 1

= 5.9

=6.2

=0.9

n = 26

This is the two tailed test .

The null and alternative hypothesis is ,

H0 :    = 5.9

Ha :      5.9

Test statistic = z

= ( - ) / / n

= (6.2 - 5.9) /0.9 / 26

= 1.70

Test statistic = z =1.70

P-value = 0.0891

= 0.025

P-value ≥

0.0891≥ 0.025

Fail to reject the null hypothesis .

There is insufficient evidence to suggest that   

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