Statistical Measures

Ratios, Proportions, Rates

To summarize:

• All three of these frequency measures are calculated in basically the same way. In practice, we use:
• a ratio to compare two independent groups,
• a proportion to compare one group with a larger one to which it belongs, and
• a rate to measure an event in a population over time.
• Ratios, proportions, and rates are used in infectious disease epidemiology to describe morbidity (disease) and mortality (death).
• The next part of this module looks at how to calculate morbidity and mortality rates.