“…Of these estimation methods, OLS regression is considered to be the most accurate (Christ, Zopluoglu, Long, & Monaghen, 2012;Good & Shinn, 1990;Parker, Tindal, & Stein, 1992;Shinn, Good, & Stein, 1989), most likely because it involves statistical estimation of the best-fitting trend line rather than a series of procedures to draw trend lines on graphed CBM data, as in the Tukey, split middle, and quarter-intersect methods. However, OLS regression is sensitive to the presence of extreme values, and methods to detect and account for extreme values are receiving increasing attention in single-case and CBM research (Brossart, Parker, & Castillo, 2011;.…”