Biological Data Analysis: Homework 6

Due Tuesday, Oct. 25

You must type this and all other homework assignments. Do not e-mail the assignment to me; turn it in early (at 322 Wolf) for a foreseeable absence, or turn it in late after an unexpected absence from class.

1. For homework 5, you looked at the normality and homoscedasticity of your data. Try to forget the results of your one-way anova; based on the normality and homoscedasticity of your data, which do you think would be most appropriate for analyzing you untransformed data: one-way anova; Welch's anova; or the Kruskal-Wallis test? Explain why you chose that test.

2. Now do a Welch's anova on the same untransformed data set that you did a one-way anova on last time. Then do the Kruskal-Wallis test on the same data set. Put the results in one table that shows the test statistic, degrees of freedom, and P-value for each test.

3. How do the results of the three tests compare? If you were evil or stupid, and looked at the three results before you decided which to choose, which one would you choose?

Optional SAS question. From now on, each homework assignment will have a SAS question. These are completely optional, only do them if you want to teach yourself SAS. You will not get extra credit, and there will not be SAS questions on the exams.

4. Do the Welch's anova and Kruskal-Wallis tests on your data set in SAS. Print your SAS program and output. If you don't get output (the .lst file), print the .log file so I can try to figure out what you're doing wrong.

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