Characteristic | Group | Test for group difference | ||
---|---|---|---|---|
 | XY | XYY | Statistic | p |
Total sample size | 60 | 64 | - | - |
Age (years) | ||||
  Mean (s.d.) | 13.1 (5) | 13.1 (6) | t = 0 | p = 1 |
  Range | 5–24 | 5–25 |  |  |
Full-scale IQ | ||||
  Mean (sd) | 117 (11) | 86 (14) | t =  − 14.1 | p < 0.0001 |
  Range | 88–144 | 53–112 |  |  |
SES | ||||
  Mean (sd) | 39 (16) | 53 (19) | t = 4.4 | p < 0.0001 |
  Range | 20–77 | 20–95 |  |  |
Gestation (weeks) | ||||
  Mean (sd) | 39.2 (2) | 38 (2) | t =  − 2.9 | p = 0.004 |
  Range | 32–42 | 31–42 |  |  |
Birthweight (kg) | ||||
  Mean (sd) | 3.55 (0.5) | 3.26 (0.6) | t =  − 2.8 | p = 0.006 |
  Range | 2.5–4.7 | 1.6–4.5 |  |  |
Time of XYY diagnosis | ||||
  Prenatal, n (%) | - | 25 (39) | - | - |
  Postnatal, n (%) | - | 39 (61) |  |  |
Vineland adaptive behavior composite score | ||||
  Mean (sd) | - | 76 (13) | - | - |
  Range | - | 42–112 |  |  |
Caregiver strain (CSQ score) | ||||
  Mean (sd) | - | 7 (3) | - | - |
  Range | - | 3–14 | - | - |