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Chapter 8   Comparing Groups

8.1   Comparing two means

8.1.1   Probabilities about sums and differences

This page gives an exercise that asks for a probability relating to the sum of difference of two independent variables.

8.1.2   Probabilities about differences

This page asks for a probability about either the difference between two single variables or two group means.

8.1.3   CI for difference between two means

Two exercises on this page ask confidence intervals about the difference between two group means based on sample means and standard deviations; the second is a little harder than the first.

8.1.4   Testing group means for equality

This page provides an exercise that gives practice in evaluating p-values for hypothesis tests and interpreting them.

8.2   Comparing two proportions

8.2.1   CI for difference between two proportions

Two exercises on this page ask confidence intervals about the difference between two group proportions based on sample proportions; the second is a little harder than the first.

8.2.2   Test about difference between two proportions

This exercise asks for the hypotheses, p-value and conclusion when testing whether two group proportions are equal, both with one- and two-tailed alternatives.

8.3   Paired data

8.3.1   2-sample or paired t-test

This exercise presents 3 different scenarios and asks whether the two means in each scenario should be compared with a 2-sample or a paired t-test.

8.3.2   Conduct paired t-test

In this exercise, you are presented with a set of paired data and asked to perform a test about whether the two means are equal.

8.4   Comparing many groups

8.4.1   Anova table formulae

The exercise on this page shows four formulae relating to an Anova table and ask you to match them with textual descriptions of how they are interpreted.

8.4.2   Anova table values

This exercise gives an analysis of variance table and asks you to find a few values from it.

8.4.3   Conclusion from Anova table

This exercise shows an analysis of variable table and asks for the conclusion, described in the context of the problem.

8.5   Association in contingency tables

8.5.1   Expected cell counts

This exercise shows a contingency table and asks for the expected cell count in one of the table cells, assuming the row and column variables are independent.

8.5.2   Chi-squared test for independence

In this exercise, the test statistic and p-value are provided for a chi-squared test applied to a contingency table. You are asked to interprete the result of the test.