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Stat Chapter 3
Displaying and Describing Categorical Data
Word | Definition |
---|---|
Frequency Table | Record totals and category names. Distribution of categorical variables. |
Pile | Count number of data values in each category of interest. |
Relative Frequency Table | Counts are expressed as percentages. Distribution of categorical variables. |
Area Principle | Each data value should be represented by the same amount of area. Equal width and equal spacing. |
Bar Chart | Show counts for each category. Distribution of categorical variables. Bars don't touch (Area Principle). |
Vertical (Y) Axis of Bar Chart | Frequency or relative frequency (100%). |
Horizontal (X) Axis of Bar Chart | Categories. |
Relative Frequency Bar Chart | Show percent for each category. |
Pie Chart | Slice into pieces proportional to the fraction of the whole. In percents, whole circle adds up to 100%. |
Contingency (Two-Way) Table | Two categorical variables shown individually distributed along each variable. Contingent on the value of the variable. Cells give counts NOT totals. |
Marginal Distribution | Distribution of one variable. From totals on margins of contingency tables. Total per category / The whole. |
Conditional Distribution | Distributions of one variable for just the individuals who satisfy some condition on another variable (restricts). Value of cell / Row or Column total. |
Independent Variable | Segmented bar chart shows IDENTICAL values. Means two variables have NO ASSOCIATION. |
Dependent Variable | Segmented bar chart shows DIFFERENT values. Means two variables ARE ASSOCIATED. |
Segmented Bar Chart | Conditional distribution of categorical variable within each category of another variable. By percents. Each bar treated as a whole (like a pie chart). |
Simpson's Paradox | When averages are taken across different groups, they can appear to contradict the overall averages. |