5.1.1—Data representation

Choose a display suited to the data: bar charts for categories, histograms for continuous intervals, and scatter plots for paired numerical variables. Axes need labels, units and honest scales.

Keep class widths visible in histograms and avoid implying continuity for categorical bars. A graph is a model of the data, not decoration.

A histogram with unequal class widths uses frequency density so each bar area represents frequency.

A histogram’s bar height is not always frequency; unequal widths require density.