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.