Table 2.
Characteristics and statistical comparison of the internal, holdout, and external validation sets
| Internal validation set | Holdout validation set | External validation set | Internal–holdout |
Internal–external |
|||
|---|---|---|---|---|---|---|---|
| Statistical test (df) | p value | Statistical test (df) | p value | ||||
| Sex (female:male) | 78:52 | 55:33 | 120:81 | χ2(1) = 0.14 | 0.71 | χ2(1) = 0.01 | 0.96 |
| Age (years) | 35.39 (14.41) | 33.78 (15.35) | 22.70 (6.83) | t(216) = 0.79 | 0.43 | t(329) = 10.76 | 2.44 × 10−23 |
| SSRT (ms) | 190 (36) | 195 (34) | 241 (49) | t(216) = −1.13 | 0.26 | t(329) = −10.31 | 8.55 × 10−22 |
| SSD (ms) | 278 (61) | 266 (66) | 284 (123) | t(216) = 1.35 | 0.18 | t(329) = −0.57 | 0.57 |
| Mean Go RT (ms) | 486 (62) | 479 (71) | 535 (105) | t(216) = 0.85 | 0.40 | t(329) = −4.79 | 2.55 × 10−6 |
| Mean failed Stop RT (ms) | 421 (58) | 409 (66) | 460 (92) | t(216) = 1.42 | 0.16 | t(329) = −4.25 | 2.79 × 10−5 |
| Number of successful Stop epochs | 22.68 (3.49) | 22.78 (3.69) | 38.85 (4.46) | t(216) = −0.22 | 0.83 | t(329) = −35.00 | 5.98 × 10−113 |
| Number of failed Stop epochs | 19.63 (3.70) | 20.16 (3.95) | 32.09 (5.11) | t(216) = −1.01 | 0.32 | t(329) = −24.02 | 2.30 × 10−74 |
| Probability of successful Stop | 0.54 (0.07) | 0.53 (0.09) | 0.52 (0.03) | t(216) = 0.51 | 0.61 | t(329) = 3.17 | 0.002 |
| Probability of Go omission | 2.49 (3.53) | 2.27 (4.16) | 0.03 (0.04) | t(216) = 0.43 | 0.67 | t(329) = 9.93 | 1.65 × 10−20 |
| Probability of choice errors | 2.33 (2.00) | 2.57 (3.37) | 0.01 (0.02) | t(216) = −0.67 | 0.50 | t(329) = 16.46 | 8.20 × 10−45 |
For all analyses, t tests were used, except for sex comparisons, for which we used a χ2 test. Means and SDs are reported, except for sex. df, degrees of freedom.