In a study of exhaust emisions from school buses, the pollution intake by passen. gets was determined for a sample of nine school buses esti in the Southern California Air Basin. The pollution intake is the amount of exhaust emissions, in grams per 1 time were person per million grams emitted, that would be inhaled while traveling on the bus during its usual 18-mile trip on congested freeways from South Central LA to a magnet the you are this school in West LA. (In comparison, a city of 1 million people will inhale a total of about 12 grams of exhaust per million grams emitted.) Here are the amounts for the nine 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 Make a stemplot. Are there outliers or strong skew-ness that would preclude use of the t procedures? A good way to judge the effect of outliers is to do your analysis twice, once with the outliers and a sec ond time without them. Give two 90% confidence intervals, one with all the data and one with the out liers 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. Compare the two intervals in part (b). What is the most important effect of removing the outliers?
1. In a study of exhaust emisions from school buses, the pollution intake by passen. gets was determined for a sample of nine school buses esti in the Southern California Air Basin. The pollution intake is the amount of exhaust emissions, in grams per 1 time were person per million grams emitted, that would be inhaled while traveling on the bus during its usual 18-mile trip on congested freeways from South Central LA to a magnet the you are this school in West LA. (In comparison, a city of 1 million people will inhale a total of about 12 grams of exhaust per million grams emitted.) Here are the amounts for the nine 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
- Make a stemplot. Are there outliers or strong skew-ness that would preclude use of the t procedures?
- A good way to judge the effect of outliers is to do your analysis twice, once with the outliers and a sec ond time without them. Give two 90% confidence intervals, one with all the data and one with the out liers 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.
Compare the two intervals in part (b). What is the most important effect of removing the outliers?
2.Our bodies have a natural elec trical field that is known to help wounds heal. Does changing the field strength slow healing? A series of experiments with newts investigated this question. In one experiment, the two hind limbs of 12 newts were assigned at random to either experimental or control groups. This is a matched pairs design. The electrical field in the experimental limbs was reduced to zero by applying a voltage. The control limbs were left alone.Here are the rates at which new cells closed a razor cut in each limb, in micrometers per hour
- Why is this a matched pairs design? Explain your answer.
- Make a stemplot of the differences between limbs of the same newt (control limb minus experimental limb). There is a high outlier.
- A good way to judge the effect of an outlier is to do vour analysis twice, once with the outlier and a second time without it. Carry out two t tests to see if the mean healing rate is significantly lower in the experimental limbs, with one test including all 12 newts and another omitting the outlier. What are the test statistics and their values? Does the outlier have a strong influence on your conclusion?
| Newt. 12 3 4 5 6 7 8 9 10 11 12 |
| Control limb. 36 41 39 42 44 39 39 56 33 20 49 30 |
| Experimental limb. 28 31 27 33 33 38 45 25 28 33 47 23 |
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