10.115 A horizontal directional drilling training was conducted for the California Department of Transportation engineers and safety inspectors.

A pretest was administered prior to the training and a final exam was given at the end of the training. Ariaratnam, Najafi, and Morones (Journal of Professional Issues in Engineering Education and Practice, 2002) reported the results, as shown in table below.

a Are the mean pretest scores significantly different for the two areas, San Bernardino and Orange County? Justify at the 5%
error rate.
b Are the mean final test scores significantly different for the two areas, San Bernardino and Orange County? Justify at the 5%
error rate.
c We are interested in determining whether there is a significant improvement in the mean scores from the pretest to the final test. Do we have sufficient information to answer this question? If yes, show your work. If no, justify why not.
d We are not sure how the engineers were selected for this training. Will it have any effect on your conclusions? Describe.
e Suppose the participants constitute all the engineers of the California Department of transportation. Will your answer to parts

(a) and

(b) change? Justify your answer.

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Pretest Results Mean Standard Final Test Results Mean Standard n Percentage Deviation Percentage Deviation Area San 53 53.05 9.66 74.39 8.34 Bernardino Orange 65 56.97 8.39 76.28 7.31 County