Car Fuel Consumption Ratings Listed below are combined city-highway fuel consumption ratings (in miles/gal) for different cars measured under the old rating system and a new rating system introduced in 2008 (based on data from USA Today). The new rating were implemented in response to complaints that the old ratings were too high. Use a 0.01 significance level to test the claim the old ratings are higher than the new ratings. Old rating 16 18 27 17 33 28 33 18 24 19 18 27 22 18 20 29 19 27 20 21 New rating 15 16 24 15 29 25 29 16 22 17 16 24 20 16 18 26 17 25 18 19 Solution Old rating: n1=20, xbar1=22.7, s1=5.37 New rating: n2=20, xbar2=20.35, s2= 4.72 The test hypothesis is Ho:1=2 Ha:1>2 The test statistic is t=(xbar1-xbar2)/[s1^2/n1 + s2^2/n2] =(22.7-20.35)/sqrt(5.37^2/20 + 4.72^2/20) = 1.47 Given a=0.01, the critical value is |t(0.01, df=n1+n2-2=38)|=2.43 (check student t table) Since t=1.47 is less than 2.43, we do not reject Ho..