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Reporting Proportions and Percentages

Numbers and Percentages

Stephen J. Lurie

and Margaret A. Winker

Reporting Proportions and Percentages

Whenever possible, proportions and percentages should be accompanied by the actual numerator (n) and denominator (d) from which they were derived. The numerator and denominator should be expressed as “n of d,” not by the virgule construction “n/d,” which could imply that the numbers were computed in an arithmetic operation.

Death occurred in 6 of 200 patients.

Not: Death occurred in 6/200 patients.

For clarity, when a numerator and denominator are accompanied by a resulting proportion or percentage, the proportion or percentage should not intervene between the numerator and denominator.

Death occurred in 6 of 200 patients (3%).

Death occurred in 3% (6 of 200) of patients.

Of the 200 patients, death occurred in 6 (3%).

Of the 200 patients, 6 (3%) died.

Not: Death occurred in 6 (3%) of 200 patients.

The denominator may be omitted if it is clear from the context.

Death occurred in 3 patients (1%).

In expressing a series of proportions or percentages drawn from the same sample, the denominator need be provided only once.

Of the 200 patients, 6 (3%) died, 18 (9%) experienced an adverse event, and 22 (11%) were lost to follow-up.

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