Radley Keith C, Dart Evan H, Wright Sarah J
Department of Psychology, The University of Southern Mississippi.
Sch Psychol Q. 2018 Jun;33(2):314-322. doi: 10.1037/spq0000243. Epub 2018 Feb 15.
Research based on single-case designs (SCD) are frequently utilized in educational settings to evaluate the effect of an intervention on student behavior. Visual analysis is the primary method of evaluation of SCD, despite research noting concerns regarding reliability of the procedure. Recent research suggests that characteristics of the graphic display may contribute to poor reliability and overestimation of intervention effects. This study investigated the effect of increasing or decreasing the data points per x- to y-axis ratio (DPPXYR) on rater evaluations of functional relation and effect size in SCD data sets. Twenty-nine individuals (58.6% male) with experience in SCD were asked to evaluate 40 multiple baseline data sets. Two data sets reporting null, small, moderate, and large intervention effects (8 total) were modified by manipulating the ratio of the x- to y-axis (5 variations), resulting in 40 total graphs. Results indicate that raters scored effects as larger as the DPPXYR decreased. Additionally, a 2-way within-subjects analysis of variance (ANOVA) revealed a significant main effect of DPPXYR manipulation on effect size rating, F(2.11, 58.98) = 58.05, p < .001, η2 = .675, and an interaction between DPPXYR manipulation and magnitude of effect, F(6.71, 187.78) = 11.45, p < .001, η2 = .29. Overall, results of the study indicate researchers and practitioners should maintain a DPPXYR of .14 or larger in the interest of more conservative effect size judgments. (PsycINFO Database Record
基于单案例设计（SCD）的研究经常在教育环境中用于评估干预措施对学生行为的影响。视觉分析是SCD评估的主要方法，尽管有研究指出该程序的可靠性存在问题。最近的研究表明，图形显示的特征可能导致可靠性差和干预效果的高估。本研究调查了增加或减少每个x轴与y轴比率（DPPXYR）的数据点对SCD数据集中功能关系评分者评估和效应大小的影响。29名有SCD经验的个体（58.6%为男性）被要求评估40个多基线数据集。通过操纵x轴与y轴的比率（5种变化）对两个报告无效、小、中、大干预效果的数据集（共8个）进行修改，最终得到40个图表。结果表明，随着DPPXYR的降低，评分者对效果的评分更高。此外，一项双因素重复测量方差分析（ANOVA）显示，DPPXYR操纵对效应大小评分有显著的主效应，F(2.11, 58.98) = 58.05，p <.001，η2 =.675，并且DPPXYR操纵与效应大小之间存在交互作用，F(6.71, 187.78) = 11.45，p <.001，η2 =.29。总体而言，研究结果表明，为了做出更保守的效应大小判断，研究人员和从业者应将DPPXYR保持在0.14或更大。（PsycINFO数据库记录）
