Data Analysis

Prevalence

Incidence

This measure the number of people in a population at risk, who have the exposure at a given point in time (current/existing case).

This measures the number of people in a population at risk, who developed the disease over a given period of time (new cases)

Point Prevalence

Period Prevalence

This is prevalence measured at one point in time.

Cumulative Incidence

Incidence Rate

  • Rate = TIME COMPONENT

This is prevalence measured over a period of time, such as a week, month, etc.

  • Expressed as a %
  • Prevalence is a proportion

Prevalence (P) = (Number of Existing Cases/Total Population) x 10n

Prevalence (P) = (Number of Existing Cases/Total Population) x 10n

  • How many people develop a disease/condition every week, month, etc.

This measure the proportion of people at risk of developing the disease during a defined period.

  • This estimates the risk of becoming diseased in the time period
  • The numerator and the denominator both exclude people with existing illness
  • This is expressed as “cases per ‘10n’ people/population” (can be %)
  • The denominator is the number of ‘persons at risk’
  • The numerator is the number of new cases

CI = (New Cases/Number of People at Risk) x 10n

  • Incidence rate has a time component, and is NOT measured as a percentage

iR = (Number of New Cases/Total Time People are at Risk) x 10n

  • Numerator is the same as cumulative incidence (new cases)

This measures the rate at which people are getting the disease.

  • However, the denominator is person-time