This study revisits Tarlow’s (2017) baseline-corrected Tau and examines key methodological issues affecting its application in single-case experimental designs. Two primary concerns were identified: the use of a two-tailed significance test for detecting monotonic baseline trend and the sensitivity of the statistic to tied values. The two-tailed approach may result in unnecessary baseline correction regardless of trend direction, while excessive tie correction can lead to underestimated effect sizes even in cases of complete nonoverlap. To address these issues, a one-tailed testing procedure was proposed to evaluate the baseline trend in a directionally meaningful manner. Additionally, a revised tie-correction method based on cross-phase tie frequencies was introduced, aligning the denominator with pairwise comparisons between baseline and intervention phases. These refinements are expected to enhance the accuracy of Tau calculations by reducing overcorrection and improving effect size estimates from a nonoverlap perspective.
