Epi: Study Design Unique Qualities

randomized control trial

• you control or manipulate the exposure

• at the individual level

community control trial

• you control or manipulate the exposure

• at the group level

cohort

• following the people over time

• you started with people who did not have the outcome → because we want to measure incidence later

• exposure-based and population-based samples

cohort: exposure-based sample

made up of subjects with a common exposure

examples: veterans, college graduates, workers exposed to lead during battery production, childhood cancer survivors

cohort: population-based sample

exposures unknown until the first period of observation (baseline) when exposure information is collected

examples: after clinical assessment, collection of biologic samples

case control

you are finding people with and without disease

cross-sectional

only one point in time but you don’t know if they have the disease unless you ask them

ecological

• group analysis

• no manipulation

prophylactic trial

prevent disease

therapeutic disease

treat, cure, or manage existing disease