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Does matching cause selection bias?
In contrast, in density or cumulative case-control studies, matching on such a variable may lead to selection bias if exposure affects the outcome, because matching variable and exposure are associated in the matched study distribution.
When would you use a matched case-control study?
The Matched Pair Case-Control Study calculates the statistical relationship between exposures and the likelihood of becoming ill in a given patient population. This study is used to investigate a cause of an illness by selecting a non-ill person as the control and matching the control to a case.
How do you stop confounding?
Strategies to reduce confounding are:
- randomization (aim is random distribution of confounders between study groups)
- restriction (restrict entry to study of individuals with confounding factors – risks bias in itself)
- matching (of individuals or groups, aim for equal distribution of confounders)
How is an analysis of a matched case control study done?
Analysis of matched case-control studies Neil Pearce1 ,2 There are two common misconceptions about case-control studies: that matching in itself eliminates (controls) confounding by the matching factors, and that if matching has been performed, then a “matched analysis” is required.
Do you have to control for confounding in a matched study?
Matching in a case-control study does not control for confounding by the matching factors A matched design may require controlling for the matching factors in the analysis However, it is not the case that a matched design requires a matched analysis
Why do you use a matched sample in a study?
Matched sampling leads to a balanced number of cases and controls across the levels of the selected matching variables. This balance can reduce the variance in the parameters of interest, which improves statistical efficiency. A study with a randomly selected control group may yield some strata with an imbalance of cases and controls.
How many cases are in a matched pair?
Enter 58 in the Exposed Cases / Exposed controls group. Enter 89 in the Exposed Cases / Not Exposed controls group. Enter 32 in the Not Exposed Cases / Exposed controls group. Enter 95 in the Not Exposed Cases / Not Exposed controls group.