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# ANOVA and F test for variance

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6. A stockbroker at Critical Securities reported that the mean rate of return on a sample of 10 oil stocks was 12.6 percent with a standard deviation of 3.9 percent. The mean rate of return on a sample of 8 utility stocks was 10.9 percent with a standard deviation of 3.5 percent. At the .05 significance level, can we conclude that there is more variation in the oil stocks?

7. The following is sample information. Test the hypothesis that the treatment means are equal. Use
the .05 significance level.

Treatement 1 Treatement 2 Treatment 3
8 3 3
6 2 4
10 4 5
9 3 4

a. State the null hypothesis and the alternate hypotheses.
b. What is the decision rule?
c. Compute SST, SSE, and SS total.
d. Complete an ANOVA table.
e. State your decision regarding the null hypothesis.

10. The manager of a computer software company wishes to study the number of hours top executives spend at their computer terminals by type of industry. The manager selected a sample of five executives from each of three industries. At the .05 significance level, can she conclude there is a difference in the mean number of hours spent at a terminal per week by industry?

Banking Retail Insurance
12 8 10
10 8 8
10 6 6
12 8 8
10 10 10