Confounding and Effect Modification Flashcards Preview

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Flashcards in Confounding and Effect Modification Deck (14):

What thre aspects much be studied before declaring a statistical association?

Counfounding or effect modification, bias, or statistical significance


Purpose of Controlling for confounders

To get a more precise estimaste of the true association btw the exposure


Ways to control for confounding

Randimization, restriction, and matching


Analysis of data stage

stratification and multivariate or matched statistical analysis


Randomization in confounding

Allocates an equal number of subjects with the known and unkown confounders into each intervention group
Strengh: likely to be sucessful with lots of ppl
weakness: sample size may mnot be large enough...


What kind of studies is randomization practical for?

Interventional Studies.


Restriction in confounding

Study participation is restricted to only subjects who do not fall within prespecified categories of confoudner..
strenth- straight fwd, does not negatively impact internal validity,
weakness- narrows criteara, harder to enroll ppl, negatively impacts generalizability


Matching in Confounding

Study subjects seleted in matched pairs related to the confounding variable to eqaully distribute confouder among each of the study groups.
stregth= intuitive... some thing greater analytic efficency
weakness- difficult to accomplish, time consuming and expensive. ... only controls for matched cofounders.


stratification in confounding

statistical anaylsis of the data by evaluating the association within various layers
stength, intuitive
weaknes- can't work for multiple co founders.


Multivariate analysis for confounding

Statistical anaylsis of the data by mathematically factoring out the effects of the confounding variables
strengths, can control for mualtiple variables
Weakness. process can cause some individuals to not clearly understand the data
linear and logistic regression
cox proportional hazards modeling


Effect Modification

A 3rd vaiable that when present modifies the magnitude of effect of an assocaition by varying it within different levels... unlike confounding an effect modifying variable shoudl be described and reported at each level of the variable rather than controlled for.


How to check for effect modification?

Compare the strata to one another.


Two main ways control fro confounding

Study design stage and analysis of data stage


Testing for confounding

1. Caculate crude outcome
2. recaculate controlling for confounder(take out all ppl with additional varaible and recaculate)
3compare the difference... more thatn 15% difference there is confounding...