Study Design Flashcards
Observational Studies
Descriptibe, analytical, ecological or correlational, cross-sectional, case-control, cohort,
Experimental Studies
Randomized controlled trials, Cluster randomized control trials, field trials, community trials
Descriptive Studies
limited to the description of the occurrence of a disease in a population and is often the first step in an epidemiological investigation.
Analytical Studies
Further by analyzing relationships between health status and other variables.
Ecological or Correlational Studies
Used for generating hypotheses
Data can be used from different populations with widely different characteristics or extracted from different data sources.
Cross-sectional (Prevalence)
Measure of the prevalence of disease
Measurements of exposure and effect are measured simultaneously
Case-control (Retrospective)
Include people with a disease of interest and a suitable control group of people unaffected by the disease or outcome variable.
Include people with a disease of interest and a suitable control group of people unaffected by the disease or outcome variable.
Investigators collect data on disease occurrence at one point in time and exposures in a previous point in time.
Odds Ratio
The association of an exposure and a disease in a case-control study is measured by calculating the odds ration which is the ratio of the odds of exposure among the cases to the odds of exposure among the controls.
Cohort (Follow-up, or incidence)
Variables of interest are specified and measured and the whole cohort is followed up to see how the subsequent development of new cases of the disease differs between the groups with and without
Provide the best information about the causation of disease and the most direct measurement of the risk of developing disease.
Randomized Controlled Trials
Patients = subjects, particular intervention, randomly allocated subjects, any differences are chance occurrences unaffected by conscious or unconscious biases of the investigators
Field Trials
participants are healthy, assumed to be at risk, data obtained from non-institutionalized people in the general pop., purpose to prevent disease, and used to evaluate interventions
Community Trials
Participants are the community, appropriate for diseases that are influenced by social conditions and for which prevention efforts target group behaviour
Ecological Fallacy
Occurs because the association observed between variables at the group level does not necessarily represent the association that exists at the individual level.
Limits of Community Trials
§ Other methods are required to ensure that any differences found at the end of the study can be attributed to the intervention rather than to inherent differences between communities.
Only a small number of communities can be included and random allocation is usually not practicable.
Random Error
Value of the sample measurement diverges - due to chance alone- from that of the true population value.
Random error causes inaccurate measures of association.
