Chapter 9, Problem 7CR

Before you solve each problem below, first categorize it by answering the following question: Are we testing a single mean or a single proportion? Assume underlying population distributions are mound-shaped and symmetric for problems with small samples that involve testing a mean. Then provide the following information for Problems 7-14.

What is the level of significance? State the null and alternate hypotheses.

Check Requirements What sampling distribution will you use? What assumptions are you making? Compute the sample test statistic and corresponding distribution value.

Find (or estimate) the P-value. Sketch the sampling distribution and show the area corresponding to the P-value.

Based on your answers in parts (a) to (c), will you reject or fail to reject the null hypothesis? Are the data statistically significant at level a?

In terpret your conclusion in the context of the application.

Note: For degrees of freedom d.f. not in the Student's t table, use the closest d.f. that is smaller. In some situations, this choice of d.f. may increase the P-value by a small amount and therefore produce a slightly more “conservative” answer. Answers may vary due to rounding.

Toys: Electric Trains TheToylot Company makes an electric train with a motor that it claims will draw an average of only 0.8 ampere (A) under a normal load. A sample of nine motors was tested, and it was found that the mean current was $\bar{x}=1.4$ A, with a sample standard deviation of s = 0.41 A. Do the data indicate that the Toylot claim of 0.8 A is too low? (Use a 1% level of significance.)