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What Works Clearinghouse, 2014
Attrition occurs when members of the initial research sample are not part of the final analysis sample, such as due to missing data or leaving the study. Both the overall sample attrition and the differences in attrition between the groups can affect the statistical equivalence of the sample and create potential for bias. The WWC has given careful…
Descriptors: Attrition (Research Studies), Statistical Bias, Randomized Controlled Trials, Models
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What Works Clearinghouse, 2013
Attrition occurs when members of the initial research sample are not part of the final analysis sample, such as due to missing data or leaving the study. Both the overall sample attrition and the differences in attrition between the groups can affect the statistical equivalence of the sample and create potential for bias. The WWC has given careful…
Descriptors: Attrition (Research Studies), Statistical Bias, Randomized Controlled Trials, Models