8–21. As the U.S. economy cools down, investors look to emerging markets to offer growth opportunities. In China, investments have continued to grow.7 Suppose that a random sample of 15 investments in U.S. corporations had an average annual return of 3.8% and standard deviation of 2.2%. For a random sample of 18 investments in China, the average return was 6.1% and the standard deviation was 5.3%. Conduct a test for equality of population means using a= 0.01.

8–22. Ikarus, the Hungarian bus maker, lost its important Commonwealth of Inde- pendent States market and is reported on the verge of collapse. The company is now trying a new engine in its buses and has gathered the following random samples of miles-per-gallon figures for the old engine versus the  new:

 

Old engine:	8, 9, 7.5, 8.5, 6, 9, 9, 10, 7, 8.5, 6, 10, 9, 8, 9, 5, 9.5, 10, 8
New engine:	10, 9, 9, 6, 9, 11, 11, 8, 9, 6.5, 7, 9, 10, 8, 9, 10, 9, 12, 11.5, 10, 7,
	10, 8.5

Is there evidence that the new engine is more economical than the old one?