Question
A major car manufacturer wants to test a new engine to determine whether it meets new air-pollution standards. The mean emission of all engines of this type must be less than 20 parts per million of carbon. Ten engines are manufactured for testing purposes, and the emission level of each is determined. The data (in parts per million) are listed: 15.6 16.2 22.5 20.5 16.4 19.4 16.6 17.9 12.7 13.9 Do the data supply sufficient evidence to allow the manufacturer to conclude t this type of engine meets the pollution standard? alpha = .01 Compute a 80% confidence interval for the average emission level of the 10 cars.
Explanation / Answer
n=10, xbar=17.17, s=2.98 =0.01, t(0.005, df=n-1=10-1=9)=-3.25 (check student ttable) (a) The test hypothesis is Ho:>=20 Ha: -3.25, we do not reject Ho. (b) Given =0.2, t(0.1, df=n-1=10-1=9)=1.38 (check student ttable) xbar±t*s/n --> 17.17 ± 1.38*2.98/sqrt(10) --> (15.87, 18.47)