The Effects of Sample Attrition on Estimates of Channeling's Impacts for an Early Sample


In the evaluation of the National Long-Term Care Channeling Demonstration, some members of the research sample were lost to the analysis due to sample attrition. Sample attrition could distort the treatment/control group comparison, depending on the type of attrition that occurred. This report investigates whether there was evidence of bias due to attrition in the preliminary estimates of Channeling's impacts. Essentially, the report describes the pattern of attrition, discusses how attrition bias might arise, outlines the statistical procedures used to correct for bias and contains the results obtained when this procedure is used to estimate the impacts of Channeling for key outcome measures drawn from the preliminary findings. The report concludes that no global patterns of attrition bias emerge from the analysis. [35 PDF pages]

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