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3 terms

Objectives
Distinguish among rates, frequencies, proportions, and ratios;
Construct crude and specific rates and differentiate these from adjusted rates;
Discuss the need for and differentiate methods of standardization of rates;
Differentiate between measures of frequency and measures of impact;
Describe the interrelationship between incidence and prevalence;
Calculate and interpret basic epidemiological measures to quantify health outcomes in the population;
Identify common indicators used to…

Ratio

It is obtained by dividing one quantity (numerator) by another (denominator) without implying any specific relationship between the numerator and the denominator.

If there are 5 apples and 10 oranges, it is expressed as follows:

5 : 10 or 5 / 10

If there are 5 apples and 10 oranges, it is expressed as follows:

5 : 10 or 5 / 10

Proportion

It is a type of ratio. It describes outcome as a reflection of a part to the whole. It is typically expressed as percentages. For example, if there are 225 people in a room and 89 of these are males, males is 89 / 225 = 0.396. Multiply the answer by 100 to get the percentage: 0.396 x 100 = 39.6%.

Rate

It is a special kind of proportion, the frequency of a specified outcome that occurs in a population during a defined period of time, divided by the average population at risk.