Multiple Bar Charts — Revision Notes

⚡ 30-Second Revision

Read legend, scale and units.
Largest bar is not necessarily fastest growth.
Percentage increase uses the starting value.
Combine counts before calculating a weighted rate.
Describe patterns without inventing causes.

2-Minute Revision

For each bar, identify its category, series and unit. Decide which metric the question requests before ranking anything. Equal gains can produce different percentage increases because starting values differ. Group percentages need underlying counts for a combined rate. Check the axis baseline and the precision of labels, then report a descriptive conclusion supported by the chart.

5-Minute Revision

A hypothetical chart shows centres P, Q and R with first-year counts 60, 100 and 150 and second-year counts 90, 130 and 180. Each gains 30, but percentage growth is 50%, 30% and 20%. R has the largest final count, while P grows fastest. The combined count rises from 310 to 400, a growth of 90/310, about 29.03%. Explain why the unweighted average of the three growth rates, 33⅓%, does not equal the combined growth rate.

Vyyuha Quick Recall

L-U-M-B: Legend, Units, Metric, Base. Read the chart before calculating.