Of particular import to this study, is collider bias originating from stratification on retreatment variables forming an embedded M or bowtie structural design. That is, rather than assume an M structural design which suggests that "X" is a collider but not a confounder, the authors adopt what they consider to be a more reasonable…

This study focused on the predictive validity of fluency measures that comprise Dynamic Indicators of Basic Early Literacy Skills (DIBELS). Data were gathered from first through third graders attending 44 schools in 9 districts or local educational agencies that made up the first Reading First cohort in Michigan. Students were administered DIBELS…