Chapter 26

Question 1

Chi-square model

Answer 1

Chi-square models are skewed to the right. They are parameterized by their degrees of freedom and become less skewed with increasing degrees of freedom. ;)

Question 2

Cell

Answer 2

A cell is one element of a table corresponding to a specific row and a specific column. Table cells can hold counts, percentages, or measurements on other variables. Or they can hold several values. ;)

Question 3

Chi-square statistic

Answer 3

The chi-square statistic can be used to test whether the observed counts in a frequency distribution or contingency table match the counts we would expect according to some model. ;)

Question 4

Chi-square test of goodness-for-fit

Answer 4

A test of whether the distribution of counts in one categorical variable matches the distribution predicted by a model. In a chi-square test of goodness-for-fit test, the expected counts come from the predicting model. ;)

Question 5

Chi-square test of homogeneity

Answer 5

Test comparing the distribution of counts for two or more groups on the same categorical variable is called a test of homogeneity. Finds expected counts based on the overall frequencies, adjusted for the totals in each group under the null assumption that the distributions are the same for each group. ;)

Question 6

Chi-square test of independence

Answer 6

A test of whether two categorical variables are independent examines the distribution counts for one group of individuals classified according to both variables. This finds expected counts by assuming that knowing the marginal totals tells us the cell frequencies, assuming that there is no association between the variables.

Question 7

Chi-square component

Answer 7

(Observed-Expected)^2/Expected ;)

Question 8

Standardized residual

Answer 8

In each cell of a two-way table, a standardized residual is the square root of the chi-square component for that cell (Obs-Exp/square root Exp) ;)

Question 9

Two-way table

Answer 9

Each cell of a two-way table shows counts of individuals. One way classifies a sample according to a categorical variable. The other way can classify different groups of individuals according to the same variable or classify the same individuals according to a different categorical variable. ;)

Question 10

Contingency table

Answer 10

A two-way table that classifies individuals according to two categorical variables. ;)