During methods of data collection, the investigator makes no attempt to manipulate or control the variable under investigation
The investigator controls an intervention to determine the effects on the outcome of interest.
Four phases of epidemiological investigation sequence by Vaughn and Morrow (1993).
1. Descriptive (Observational), 2. Analytic epidemiology, 3. Intervention or experimental epidemiology, 4. Evaluation epidemiology.
Descriptive (Observational) epidemiology
It defines the problem in terms of characteristics of person, place, and time.It does not attempt to seek relationships between factors under investigation. It is particularly useful in generating questions for future research or alerting us to the presence of a problem within the community.
It analyzes the causes or determinants of health states. It evaluates potential associations between risk factors and health outcomes.
Intervention or experimental epidemiology
The focus is on answering questions about the effectiveness of interventions for controlling diseases or for improving underlying conditions. Rather than simply observing phenomena as in the first two phases, here the investigator is able to manipulate factors under study. It seeks to determine answers about cause-and-effect relationships.
It measure effectiveness. It determines whether these services and programmes have had a positive effect on the health status of the community.