12.1 What’s wrong? In each of the following, identify what is wrong and then either explain why it is wrong or change the wording of the statement to make it true.

  1. (a) ANOVA tests the null hypothesis that the sample means are all equal.

  2. (b) A strong case for causation is best made in an observational study.

  3. (c) You use ANOVA to compare the variances of the populations.

  4. (d) A multiple-comparisons procedure is used to compare a relation among means that was specified prior to looking at the data.