# Prevalence

## The number of cases that exist in a given population

Prevalence is defined as the number of current cases in a given population. Prevalence is a retrospective measure because it is generated using a

When calculating prevalence, the

**design. The odds ratio with 95% confidence interval is used as a measure of association and is closely tied to comparing prevalence between sub-groups and sub-populations. Although the two terms are at times used interchangeably, prevalence is different from**__cross-sectional__**because it is established in**__incidence__**, while incidence is calculated in**__retrospective designs__**.**__prospective studies__When calculating prevalence, the

__of the outcome dictates what statistic is used. If the outcome is categorical, then frequency statistics are used to establish the percentage (%) of the sample (population) that possesses the outcome of interest. With ordinal outcomes, researchers report medians and interquartile ranges as a measure of prevalence. Finally, for continuous outcomes, means and standard deviations are used to describe prevalence.__**scale of measurement**Click on the

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