Draw and interpret statistical charts including bar charts, pie charts, frequency polygons, stem-and-leaf diagrams, box plots and histograms with unequal class widths (histograms at Higher tier).

What this dot point is asking

The Eduqas statistics content asks you to draw and interpret a range of statistical charts: bar charts, pie charts, frequency polygons, stem-and-leaf diagrams, box plots, and at Higher tier histograms with unequal class widths. Each display suits a different kind of data and answers a different question, so choosing and reading the right one is the core skill. Pie-chart angles and box-plot comparisons appear at both tiers, while the histogram with frequency density is a signature Higher-tier topic because of the unequal-width subtlety.

Bar charts and pie charts

These two are the most common displays for categorical or discrete data.

For a pie chart, the reliable method is to find the angle per item ($\dfrac{360^\circ}{\text{total}}$) and multiply by each frequency. To read a pie chart back, reverse this: a $90^\circ$ sector is a quarter of the total.

Frequency polygons and stem-and-leaf diagrams

A frequency polygon plots the frequency against the midpoint of each class and joins the points with straight lines, which is useful for showing the shape of a distribution and comparing two distributions on the same axes. A stem-and-leaf diagram splits each value into a stem (the leading digits) and a leaf (the final digit), keeping the raw data while showing its shape; an ordered stem-and-leaf diagram makes the median and range easy to read directly.

Box plots

A box plot (box-and-whisker diagram) summarises a distribution using five numbers.

Box plots are ideal for comparing two distributions: a higher median means typically larger values, and a wider box (larger interquartile range) means more spread. As with all comparisons, describe the difference in context.

Histograms with frequency density (Higher)

A histogram looks like a bar chart but is fundamentally different when class widths are unequal.

The defining point is that area, not height, gives the frequency, which is why histograms (unlike bar charts) have no gaps and are used for continuous, unequally grouped data.

Why charts matter

Choosing and reading statistical displays is a practical skill used across science, geography and the media, and Eduqas tests both the construction (drawing accurately) and the interpretation (reading values, comparing distributions). The histogram is the conceptual high point because it forces the distinction between frequency and frequency density, so understanding that area represents frequency is the key to the Higher-tier marks.