Study Design Elements
Study Design Element 1: Identify the Population
The first key element in study design that uses observation of individuals is to identify the population that is the study base.
Study Design Element 2: Sampling
The second key element in study design is best thought of as ways of sampling the disease experience of a cohort or study base or reference population.
Study Design Element 3: Timing of Measurements
The third key element in study design is the timing of measurements of the predictor variables and the outcome variables relative to the time period of the experience of the study base.
Confusion About Timing of Measurements
There is much confusion around applying the terms retrospective and prospective to study designs.
- If you focus on when the measurements were made in relation to when the disease outcome was measured or detected, you will avoid confusion about which came first.
- The timing of the measurements should be looked at separately from the timing of carrying out the study.
- A study may be carried out after the disease outcomes have occurred but use measurements that were made before they occurred.
Jeff Martin, MD
-- MaryB - 12 Feb 2009