“…Although a functional relationship does imply a "robust" independent variable (Baer, 1977), it does not quantify the effect size as the Percentage of Non-Overlapping Data (PND; Scruggs & Mastropieri, However, because the group design quality indicators checklist did not include an assessment of intervention "effects," we did attempt to calculate effect sizes for the six group studies used in our review (i.e., Bates, Cuvo, Miner, & Korabek, 2001;Izzo, Cartledge, Miller, Growick, & Rutkowski, 2000;Martin et al, 2006;Nelson, Smith, & Dodd, 1994;Sinclair, Christensen, and Thurlow (2005); Van Reusen & Bos, 1994). Using Cohen's d, effect sizes were d = 0.334 (Self -Advocacy Strategy; Van Reusen & Bos, 1994), d = 0.588 (extending services beyond secondary school; Izzo et al, 2000), and d = 1.53 (teaching job applications; Nelson et al, 1994). Effect sizes for the other three studies were not, or could not be, calculated.…”