Table II.
Bayley-II and Wechsler Scores and Prevalence of Cognitive Impairment (N = 1,429)
| Test | Na | FSIQ/MDI | VIQ | PIQ | VC | PO | FD/WM | PS |
|---|---|---|---|---|---|---|---|---|
| BSID-II | ||||||||
| Mean (SD) | 30 | 83 (15) | ||||||
| Percentage with score <70 | 20 | |||||||
| WPPSI-R | ||||||||
| Mean (SD) | 188 | 84 (14) | 84 (14) | 87 (15) | ||||
| Percentage with score <70 | 13 | 15 | 10 | |||||
| WISC-III | ||||||||
| Mean (SD) | 1188 | 85 (17) | 84 (16) | 88 (17) | 85 (16) | 88 (17) | 86(16) | 93(17) |
| Percentage with score <70 | 17 | 18 | 13 | 18 | 13 | 16 | 8 | |
| WAIS-III | ||||||||
| Mean (SD) | 36 | 87 (16) | 86 (16) | 91 (16) | 89 (17) | 92 (18) | 83 (15) | 86(13) |
| Percentage with score <70 | 11 | 14 | 6 | 3 | 6 | 26 | 12 | |
| Overall | ||||||||
| Mean (SD) | 1429 | 85 (16) | 84 (16) | 88 (17) | 85 (16) | 88 (17) | 86 (16) | 93(17) |
| Percentage with score <70 | 16 | 17 | 13 | 17 | 13 | 16 | 8 | |
| Z-statisticb | 33.17++ | 35.52++ | 24.12++ | 32.92++ | 22.34++ | 29.89++ | 8.98++ | |
| T-statisticc | 36.07++ | 37.22++ | 27.70++ | 31.67++ | 23.77++ | 29.75++ | 11.02++ |
Cognitive impairment defined as standard score <70.
aMaximum number with any single test score.
bThis corresponds to the upper-tailed one-sample z-test for the true proportion of impairment in this population (p-value <.05 implies impairment rate is significantly higher than the general population rate of 2.5%).
cThis corresponds to the lower-tailed t-test for the true mean score (p-value <.05 implies mean score is significantly smaller than the general population mean of 100).
++p < 0.01, one-tailed.