Question 14.71

14.71 Analyzing contrasts.

Return to the eyes study in Example 14.13 (pages 729–731). Answer the following questions for the two contrasts that you defined in Exercise 14.69.

  1. For each contrast give and an appropriate . In choosing the alternatives, you should use information given in the description of the problem, but you may not consider any impressions obtained by inspection of the sample means.

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  2. Find the values of the corresponding sample contrasts and .
  3. Using the value , calculate the standard errors and for the sample contrasts.
  4. Give the test statistics and approximate -values for the two significance tests. What do you conclude?
  5. Compute 95% confidence intervals for the two contrasts.

14.71

For part a: (a) . (Arguments could be made for a one-sided alternative as well.) (b) . (c) . (d) . There is not enough evidence that the average score of the brown eyes is different than the average score of the other two eye colors. (e) . For part b: (a) . (Arguments could be made for a one-sided alternative as well.) (b) . (c) . (d) . There is not enough evidence that the average score when the model is looking at you is different than the average score when the model is looking down. (e) .