Describing categorical data
Frequency and relative frequency, pie and bar charts, Pareto charts, misleading graphs, mode and ordinal median.
Study sections
Follow the order or choose a sectionFrequency tables: count each category
A frequency is a count. A frequency distribution lists the different categories and how many observations belong to each. It turns a lo…
02Relative frequency: compare fairly
Raw counts can be hard to compare when groups have different sizes. Relative frequency tells us what fraction of a group belongs to a c…
03Pie charts: show parts of one whole
A pie chart is a circle split into slices. Each slice has an area proportional to its category’s share. The entire circle represents th…
04Bar charts, Pareto charts and category order
A bar chart compares categories using bar lengths. You can display counts, relative frequencies, or percentages. Tell the reader which…
05Read charts carefully: avoid misleading graphs
A chart should make the data easier to understand. Its appearance should not exaggerate a difference, hide a category, or make a differ…
06Mode and median: most common versus middle
A descriptive measure is a compact summary of a dataset. Measures of central tendency describe a center or typical value. For categoric…