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40 Cards in this Set
- Front
- Back
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two critical questions in epi
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1) internal validity- is the study believable
2) external- if so can the results be tied with the genersal public |
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works by taking a national samploe
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external validity
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what are the 3 alternative explanations that must be eliminated during test process
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1) confounding
2) bias 3) other things |
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cruse and adjusted rate make up __________?
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confounding
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how does one determine whether confoundinng is present or not?
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compare crude rate and relative risk or odds ratio
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exposure? outcome?
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e= gender race ethnicity
o= speed (what u want to know) |
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what are some potential confounders?>
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age, height, for speed
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nuissance variables?
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confounding variables
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whiich variables are usually confounders?
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usually risk factors for the disease
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steps for contolling for confounding?
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1) randomization
2) restriction 3) matching 4) stratification 5) multivariable analysis |
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what is randomization?
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must have sufficient sample size, randomization controlls for both known and unknown
--* limited *-- only experimental |
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what is restriction?
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restricts certain categories
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controllling for confounders in the design phase GOAL
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elemiinater or reduce variation between compared groups
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a drawback of restriction
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limits generalizability
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what is def of matching when controllling for confounders?
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distribut confoundiing factors in an identical manner
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2 x 2 data table is used to calculate what of what?
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odds ratio of total data
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what are the limitations of stratification?
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difficult to control for many variables simultaneously
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what is a not how to way to control for confounding?
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multivariate
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what are teh design and analysis factors to confounding?
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design- randomization, restriction, matching
analysis- stratification, multivariate analysis |
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the third variable that mixes the effects between exposure and and outcome
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confounder
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CONFOUNDING-
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1.make a comparison if crude rate and average of strata look sor a 10 % difference
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this unlike confounding should be reported and described and not controlled
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effect measure modification
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relative risk
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used in a cohort study to analyze
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odds ratio?
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used for case control studies to analyze
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what are both ways to assess effect measure modification?
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1. visually
2. statistical test--chi squared |
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witth effect measure stratification
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u compare the two strata
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A C
B D relative risk? |
A/C & B/D
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odds ratio?
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a/d / b/c
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null hypothesis
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equal
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alternative
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not equal
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if you are controlling for the confounding
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report the adjusted measure of modification
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if u want to say there is a difference in the strata?
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report the measure of association for each strata
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the mixing of effects between and exposure of association of each strata
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effect measure modification
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bias
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systmeatic error of inference
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bias toward null
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effects are underestimated
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bias away from null
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effects are overestimated
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what kind of error can happen in all study types
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bias
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what is in a case cobntol study
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selection bias
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giw else can y get selection bias
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prospectve cohort and experimental atudies
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BIAS dor case control
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berkson and neyman
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