Representing Data

This unit covers the diagrams used to present data, including tally charts, two-way tables, pictograms, bar charts, pie charts, stem-and-leaf diagrams, line graphs, histograms, frequency polygons, cumulative frequency, population pyramids and misleading graphs.

Each diagram has conventions that carry marks independently of the data — bar charts need gaps and labelled axes, histograms have touching bars and require frequency density when class widths are unequal, and cumulative frequency points go at the upper class boundary rather than the midpoint. That last point is the most common error in the unit. Questions about misleading graphs are examined regularly and reward naming the specific fault and explaining the false impression it creates, rather than simply calling a diagram misleading.