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The number of new cases of a disease in a population during a stated period.

The number of new cases of a disease occurring in a population during a stated period.

For example, an investigation might ask whether people exposed to a possible risk factor have a higher incidence of a disease than people who are not exposed. Researchers could use surveys or medical records rather than examining every member of the population.

Compare incidence as a proportion or rate when groups contain different numbers of people; raw case totals may be misleading.

When comparing places or years, use incidence rates rather than raw case numbers, because population sizes may differ.

Do not write that a risk factor guarantees disease. State that it changes the probability or incidence.

The number of new cases of a disease occurring in a population during a specified period, often expressed as a rate such as cases per 100,000 people per year.

Incidence is the number of new cases appearing in a population during a stated period.

The number of new cases of a disease in a defined population during a stated period.

To investigate how often it develops, we look at incidence: the number of new cases in a defined population over a stated time. This differs from the number of people already living with the disease. An incidence rate, such as new cases per 100,000 people per year, makes populations of different sizes easier to compare.

Incidence

Definition

How each exam board covers it

AQA GCSE Biology · 8461

Exam tips

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OCR GCSE Biology A · J247

OCR GCSE Biology B · J257