Cumulative Frequency & Interquartile Range

Build up a running total of frequencies to find medians, quartiles and spread.

Box Plots (Box-and-Whisker Diagrams)

Draw and interpret box plots using the five-figure summary — minimum, LQ, median, UQ and maximum — with worked examples from Nova.

Cumulative Frequency Curves

Build a cumulative frequency table, plot the curve correctly, and use it to read off median and quartile estimates.

Interquartile Range

Find the lower quartile, upper quartile and interquartile range from a cumulative frequency curve — and why IQR is better than the range.