Unit 2 Flashcards
What are the two types of study designs?
descriptive, explanatory
Intended to describe a disease condition - signs, lesions, outcomes, occurrence of microbes, etc.
Descriptive study
Seeks to identify causes. Has a hypothesis, has controls. Used to investigate a treatment, intervention, or risk factor, in hopes of providing causal evidence.
Explanatory (or causal) study
List the two main types of explanatory studies:
experimental, observational (epidemiologic)
List the three types of observational studies:
cohort
case control
cross sectional
Planned comparison between 2 groups - one receiving one treatment, another receiving a different tx for a naturally disease - researcher has some control
Experimental - Clinical trials
Researcher has the greatest control and involves the use of experimental animals. This type of study is the best design to prove cause or demonstrate efficacy
Experimental - laboratory
Sometimes called “natural studies” as they occur freely in nature.
Observational studies
Why are observational studies under the category of “explanatory type” studies?
the goal is to assess cause
What is the difference between observational and experimental studies?
Which animals go to treatment groups is not under control of the researcher for observational
Observational studies contribute to the body of evidence implicating a ______ as a cause. They often do not provide sufficient ________, in one study, to establish a cause.
factor; evidence
a group sharing a defining characteristic
cohort
Type of observational study that is prospective in time:
cohort
What are the two types of cohorts featured in a study?
- one exposed to a factor
2. one NOT exposed to a factor
Subjects are followed in time, and incidence of one or more diseases are compared between the two groups:
cohort
For a cohort study, what does a relative risk >1 indicate?
an increased risk in exposed, compared to unexposed
For a cohort study, what does a relative risk =1 indicate?
that the risk in exposed is the same as the risk in the unexposed
For a cohort study, what does a relative risk <1 indicate?
that the disease in the exposed is less than the unexposed
A relative risk < 1 for a cohort study indicates that exposure has a “sparing effect”. What does this mean?
a reduction in risk associated with exposure
What kind of exposures might give a sparing effect?
vaccinations
Measure of the strength of association between a factor and a disease:
relative risk
Relative risk can ONLY be calculated in what 2 studies?
cohort and cross-sectional
Cannot be estimated in a case-control study:
relative risk
What is the equation for relative risk?
(proportion with disease in exposed)/(proportion with disease in unexposed)