Study Designs and Measures of Association Flashcards
Define a cohort study.
Comprises of people with common characteristic.
Exposed and unexposed cohorts.
Purpose of cohort is to measure occurrence of one of more specific diseases during follow-up with aim of comparing disease rates.
What is an experiment?
A study in which incidence rate or risk of disease in two or more cohorts is compared after assigning exposure to people.
What is the aim of a clinical trial?
To evaluate the incidence rate of disease complications in cohorts assigned to difference treatment groups. through randomization.
What is incidence rate?
Number of new persons developing disease within a time period / person years.
What is a field trial?
Test whether intervention works in real life settings.
What is community intervention trial?
Exposure is assigned to groups of people rather than individuals.
What is one requirement of a population at risk?
They must all be free of disease at outset.
What is the difference between a closed an an open cohort?
A closed cohort has a fixed membership. Once members are identified, there can be no new members. Will always become shorter with time.
An open cohort can take additional members as time passes.
How do you count disease events in a closed versus open cohort?
Closed cohort: risk.
Open cohort: incidence rate.
Define a case-control study.
Two groups differing in outcomes are identified and compared on the basis of a supposed causal attribute.
What is the purpose of a case control study?
To determine if exposure is associated with an outcome.
What is calculated from a case control study?
Odds ratios.
What is a case crossover study?
Each PPT acts as their own control. Control is a sample of time before exposure.
What is a longitudinal study?
Information pertains to more than one point in time. It is implicit that the causal action comes before the development of the disease as consequence to exposure.
All cohort studies are longitudinal.
What is a cross-sectional study?
Measures prevalence of characteristics. Cannot measure incidence because risk calculation requires information across time.
What do case control studies help us answer?
If QUANTITY of one variable is different based on value of another.