Answer to Question #325053 in Statistics and Probability for Akib

Question

The hydrocarbon emissions at idling speed in

parts per million (ppm) for automobiles of 1980 and

1990 model years are given for 20 randomly selected

cars.

1980 models:

141 359 247 940 882 494 306 210 105 880

200 223 188 940 241 190 300 435 241 380

1990 models:

140 160 20 20 223 60 20 95 360 70

220 400 217 58 235 380 200 175 85 65

(a) Construct a dot plot as in Figure 1.1.

(b) Compute the sample means for the two years and

superimpose the two means on the plots.

(c) Comment on what the dot plot indicates regarding

whether or not the population emissions changed

from 1980 to 1990. Use the concept of variability

in your comments.