SL 4.2—Data presentation

Choose a display that preserves distribution and comparison.

Frequency tables organise discrete or continuous data; equal-class-width histograms show continuous frequency, cumulative-frequency graphs locate medians, quartiles and percentiles, and box plots compare centre, spread, symmetry and outliers.

Example

If a cumulative-frequency graph for 80 values gives $Q_1=18$ and $Q_3=30$, then $IQR=12$ and the outlier fences are $0$ and $48$. Mark any value outside those fences with a cross on the box plot.

Read class inequalities without gaps, use the cumulative total to locate the required percentile, then compare box plots using median, IQR, range, symmetry and outliers.

For this syllabus section, frequency-density histograms are not required; a scatter plot belongs to bivariate correlation, not one-variable distribution display.