Block 1: Epidemiology
EPI3-4: FOUR MEASURES OF EFFECT: THE PREVALENCE RATIO

SESSION OBJECTIVE

At the end of this session you will be able to compare disease prevalence in two populations by means of a ratio of the two prevalences.

PREVALENCE:

The prevalence, P is defined as:

The prevalence corresponds to the proportion of the population that has the disease or condition at a certain point in time. Like all proportions it is dimensionless and can never take values less than 0 or greater than 1.

PREVALENCE RATIO:

The Prevalence Ratio is given by:

Example:

A factory with 10200 workers was divided up into high noise and low noise zones where 2000 and 8200 workers worked respectively. After screening 150 workers in the high noise zone and 50 workers in the low exposure zone were found to have noise-induced hearing loss. The prevalence ratio for noise-induced hearing loss was




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General Introduction to Occupational Health: Occupational Hygiene, Epidemiology & Biostatistics by Prof Jonny Myers is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 South Africa License
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