EPI7-1: STUDY DESIGN: Descriptive Versus Analytic Studies

TYPES OF STUDIES:

Many textbooks use a classification of studies into descriptive and analytic types but the distinction is quite blurred.

The moment one begins to look at change in any outcome for instance with any exposure or other variable (like age, income, or time etc.) one has moved into analytic mode.

Simple descriptive studies include:

• case series;
• prevalence studies, where only occurrence measures are used in isolation.

Although simple surveillance data (cases, rates, proportions) seem to be descriptive, once one starts to look at these in terms of the duration of time during which they were collected or at time trends one has passed over into analytic mode.

Analytic study designs include:

• prevalence or cross sectional studies;
• case control studies;
• longitudinal, cohort or follow up studies.

The above study designs have as their basic unit of analysis the individual.

There are other types of studies, termed ecological studies, where differences are examined at the group level. An example of the latter is comparing the mortality from liver cancer in countries with different average intakes of alcohol per capita. No individual data are measured.

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