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. Author manuscript; available in PMC: 2016 Jan 31.
Published in final edited form as: Curr Psychiatry Rev. 2015 Feb 1;11(1):19–31. doi: 10.2174/1573400510666140929195441

Table 2.

Proportion of False Positives Sudden Gains for Three Criterion Sets

Repeated BDI measures Retest r = .90 Retest r = .80 Retest r = .70
T99 G03 K05 T99 G03 K05 T99 G03 K05
Population with no change in BDI scores
10 .046 .055 .106 .092 .111 .348 .117 .143 .520
15 .079 .087 .140 .153 .170 .442 .193 .217 .637
20 .110 .119 .166 .215 .231 .498 .267 .290 .710
Population with gradual linear decreases in BDI scores
10 .182 .199 .182 .289 .322 .463 .325 .368 .625
15 .332 .347 .198 .491 .514 .478 .529 .561 .642
20 .470 .482 .177 .642 .662 .418 .683 .707 .564
Population with gradual log-linear decreases in BDI scores
10 .296 .411 .238 .434 .564 .484 .457 .587 .613
15 .389 .494 .257 .554 .662 .513 .584 .688 .638
20 .459 .558 .267 .638 .733 .512 .673 .759 .639

Note. N = 10,000 per table cell. BDI = Beck Depression Inventory. T99, G03, and K05 are sudden-gains criteria presented by Tang and DeRubeis [5], Gaynor et al. [19], and Kelly et al. [23], respectively. Sudden gains are drops in BDI scores between adjacent measurements that are (a) at least 7 points, (b) at least 25% of the pre-gain score, and (c) relatively stable. As detailed in the Method, criterion (c) is variously defined as a significant t-test comparing pre- and post-gain score means (Tang et al.); maintenance of at least 50% of the gain across the next two scores (Gaynor et al.); or a drop in scores at least 1.5 times the standard deviation of the patient’s entire series of scores (Kelly et al.). Expected values in each cell are .025 based on nominal alphas of .05, two-tailed, for hypothesis tests.