Question

In a study of exhaust emissions from school buses, the pollution intake by passengers was determined for a sample of 9 school buses used in the Southern California Air Basin. The pollution intake is the amount of exhaust emissions, in grams per person, that would be breathed in while traveling on the bus during its usual 18-mile trip on congested freeways from South Central LA to a magnet school in West LA. (As a reference, the average intake of motor emissions of carbon monoxide in the LA area is estimated to be about 0.000046 grams per person.) Here are the amounts for the 9 buses when driven with the windows open

1.15 0.33 0.40 0.33 1.35 0.38 0.25 0.40 0.35

a) Make a stemplot. Are there outliers or strong skewness that would forbid use of the t procedures?

b) A good way to judge the effect of outliers is to do your analysis twice, once with the outliers and a second time without them. Give two 90% confidence intervals, one with all the data and one with the outliers removed, for the mean pollution intake among all school buses used in the Southern California Air Basin that travel the route investigated in the study.

c) Compare the two interval in part (b). What is the most important effect of removing the outliers?

Answer 1

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