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…

Teacher aides, teachers, administrators, and observers in 1 elementary, 1 junior high, and 1 senior high school participated in an evaluation of the effectiveness of the Detroit Pilot Program to Train Teacher Aides in (1) identifying, developing, and defining the role of the aide and (2) identifying effective aide training methods. Procedures…