Gearing up to address attrition: Cohort designs with longitudinal data

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As education researchers we know that one of the greatest threats to our work is sample attrition – students dropping out of a study over time. Attrition plays havoc with our carefully designed studies by threatening internal validity and making our results uncertain. To gear up for our evaluation of the Pennsylvania State Gaining Early Awareness and Readiness for Undergraduate Programs (GEAR UP), we designed a three-pronged approach to handling sample attrition. We describe it here in case it can be helpful to others.