EPIB301: Intro to Study Designs

Descriptive study, analytical study, observational, experimental, meta-analyses, anecdotal evidence

What is a study design?

A plan for data collection, analysis, and interpretation that involves a formal approach to scientific investigations. Directs how an epidemiological investigation is conducted.

What are the characteristics of descriptive studies?

Addresses “who, when, and what” questions and describes the occurrence of exposures and outcomes. It also only generates hypotheses and does not do formal testing.

What are the characteristics of analytic studies?

Addresses “how and why” questions and assesses the association between exposure and outcomes. This design also tests the research question.

What are the characteristics of the general classification of observational?

Exposures occur in a “non-controlled” environment, and researchers observe relationships among variables

What are the characteristics of the general classification of experimental?

Researchers have control over the exposure and who is exposed

What are the characteristics of the general classification of meta-analysis?

Combines the results of several studies that address a set of related research hypotheses

What does the manipulation of study factor (M) determine?

Whether or not a study design was controlled by investigators

What does randomization of study subjects (R) determine?

Whether or not a study design used a random process to determine exposure

What includes both manipulation and randomization?

Experimental

What does not include both manipulation and randomization?

Observational

What are the characteristics of anecdotal evidence?

Based on individual descriptions/reports of personal experiences or observations. They are often used in arguments and daily conversations, not collected in a scientific way.

What are the issues with anecdotal evidence?

• Based on the individual

• Not representative of a population

• Low reliability

• “Cherry-picking”

• Not tested by statistics

• High potential for bias

• Humans are more likely to remember notable or unusual examples

What are the aspects of study designs?

Data collection, number of observations, unit of observation, directionality (time), sampling, measures

What aspect of study design follows this: primary (collect new) or secondary (use existing)?

Data Collection

What aspect of study design follows this: single time point or multiple time points?

Number of Observations

What aspect of study design follows this: individuals or groups?

Unit of Observation

What aspect of study design follows this: reverse (retrospective) or forward (prospective)?

Directionality (Time)

What aspect of study design follows this: population-based or special groups (cases, exposures)?

Sampling

What aspect of study design follows this: Odds ratio, prevalence, correlation or incidence, relative risk, attributable risk?

Measures