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Download full textWhat 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
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
What Works Clearinghouse, 2014
The study reviewed here examined the effect of charter schools on annual student achievement growth in reading and math in 25 states, the District of Columbia, and New York City. The study primarily used data on students in grades 3-8, but additional elementary and high school grades were included for several states. The authors reported that…
Descriptors: Charter Schools, Academic Achievement, Correlation, Achievement Gains
