Lecture 4 - Observational studies Flashcards
Observational studies have high ___ validity
external
What are the pros of that overlap btw case reports and case series
new disease to attention, high lights unusual findings, discovers new side effects and mutations
which observational study plays a role in human tetralogy?
case reports and series
what are the pros of case series
characterize rare diseases
What are the cons of case reports
not generalizable, not based on systemic studies, associations may have other explanations
what are the cons of case series
subject to selection bias, no control, not generalizable
what are the cons of retrospective
relies on availability and accuracy of data records
for cases, ______ cases are preferred to ______ cases
incident cases are preferred to prevalent cases
What are the pros of case control study
useful for studying multiple exposure factors and rare diseases, inexpensive
what are the cons of case control study
cant estimate incident or exposure rate, difficult to estimate temporality
what is temporality
did exposure come before disease or vice versa?
define one to many matching
Matching multiple controls to each case.
define group matching
select controls based on the proportion of a characteristic in the cases
what are the pros of matched case control
removes risk factors (confounders) that may not be evenly distributed
what are the cons of matched case control
inefficient, hard to find controls, overmatching, cant study matched variables
Define over matching
matching on variables that arent of interest
Define odds
probability an event will occur/probability an event wont occur
Define odds ratio
odds of a case being exposed compared to odds of a control being exposed
interpret an odds ratio
the odds of getting a disease if you did the exposure was ___x that of someone who didnt do exposure
OR>1
positive association, therefore harmful
OR<1
negative association, therefore protective
Matched pairs can be ____ or ___-
concordant or discordant
define concordant
both case and control are exposed or unexposed
define discordant
either case/control is exposed and the other isnt
the 2x2 table of matched pair odds ratio emphasized what?
exposure
Matched pair odds ratio only determines ratio of
discordant pairs
What is the equation for odds ratio matched pair?
case exposed:controls not exposed / case not exposed:controls exposed