AP Statistics Chapter 12

two-way table

A table containing counts for two categorical variables. It has r rows and c columns.

one-way table

Table used to display the distribution of a single categorical variable.

observed counts

Actual numbers of individuals in the sample that fall in each cell of the one-way or two-way table.

expected counts

Numbers of individuals in the sample that would fall in each cell of the one-way or two-way table if H₀ were true.

chi-square test statistic

Measure of how far the observed counts are from the expected counts. This value is equal to Σ(Observed Count - Expected Count)² ÷ Expected Count.

chi-square distribution

A distribution that is defined by a density curve that takes only non-negative values and is skewed to the right.

Large Counts condition for a chi-square test

It is safe to use a chi-square distribution to perform calculations if all expected counts are at least 5.

multiple comparisons

Problem of how to do many comparisons at once with an overall measure of confidence in all our conclusions

chi-square test for goodness of fit

A test of the null hypothesis that a categorical variable has a specified distribution.

chi-square test for homogeneity

A test of the null hypothesis that the distribution of a categorical variable is the same for two or more populations/treatments.

chi-square test for independence

A test of the null hypothesis that there is no association between two categorical variables in the population of interest.

components

Individual terms that are added together to produce the test statistic χ²