M.4—Averages, ratios, percentages and experimental error

Use the statistic or percentage that matches the question, and express experimental error relative to the measured quantity.

State the denominator for a percentage change and keep ratios in a comparable form.

A 2-unit change from 10 is 20%, while the same change from 100 is 2%; the absolute change is identical but the relative change differs.

Percentage error is not the same as percentage change between two biological treatments.