Answer Happy

c. Hydrocarbon emissions from cars are known to have decreased dramatically during the 1980s. A study was conducted to compare the hydrocarbon emissions at idling speed, in parts per million, for automobiles from 1980 and 1990. Twenty cars of each model year were randomly selected, and their hydrocarbon emission levels were recoded. The data are as follows: 1980 models 1990 models 141 494 200 190 140 60 220 380 359 306 223 300 160 20 400 200 247 210 188 435 20 95 217 175 940 105 940 241 20 360 58 85 882 880 241 380 223 70 235 65 Test the hypothesis that the variances are equal and also the same normal population.