The hydrocarbon emissions at idling speed in parts per million (ppm) for automobiles of 1980 and 1990 are given for 20 randomly selected cars.

(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 you comments.

Transcribed Image Text:

1980 models: 141 247 940 494 105 880 359 306 882 210 435 380 223 200 188 940 190 300 241 241 1990 models: 20 20 95 20 140 223 60 360 70 160 380 200 220 400 217 235 58 65 175 85