TABLE 1.
Descriptive Statistics for All Variables by Grade
| Variable | 6a M (SD) | 7b M (SD) | 8c M (SD) | 9d M (SD) | 10e M (SD) | 11f M (SD) | 12g M (SD) |
|---|---|---|---|---|---|---|---|
| Age (years) | 11.3 (.5) | 12.5 (.6) | 13.6 (.6) | 14.6 (.6) | 15.6 (.7) | 16.7 (.6) | 17.6 (.7) |
| GMRC | 775.5a (160.6) | 784.6a (164.8) | 852.0b (132.7) | 878.9b (182.6) | 996.5c (140.6) | 983.1c (143.4) | 1016.4c (160.6) |
| TOWRE | 102.7a (12.2) | 98.2a,b (12.4) | 95.5b,c (11.3) | 94.5b,c (12.2) | 92.5c (12.1) | 90.2c,d (10.7) | 87.6d (9.9) |
| WJIIINR | 12.7a,c (2.5) | 12.4a (3.1) | 13.7a (3.5) | 13.7a,b (3.5) | 13.6a,b (2.9) | 13.7a,b,c (3.6) | 14.2b (3.3) |
| SSRT | 317.9a (83.1) | 306.4a,b (104.8) | 281.5a,b,c (84.8) | 278.8b,c (93.7) | 278.8b,c (93.7) | 275.9c (108.3) | 275.3b,c (99.9) |
| SSINT | 183.2a (48.6) | 180.7a (46.2) | 176.8a (46.9) | 173.8a (46.8) | 173.8a (46.8) | 180.3a (48.7) | 184.7a (46.6) |
| SSOE | 1.6a (2.3) | 1.6a (3.1) | 1.1a (2.2) | 1.3a (2.8) | .9a (2.0) | 1.1a (2.4) | 1.3a (3.1) |
| SSGRT | 772.0a (135.0) | 753.4a (146.5) | 773.6a (153.6) | 776.7a (164.9) | 772.9a (170.5) | 766.7a (164.1) | 792.6a (178.3) |
| SSRTV | 181.6a (47.4) | 179.1a (45.1) | 176.9a (41.9) | 175.5a (46.4) | 172.9a (46.4) | 179.3a (48.5) | 183.4a (46.8) |
| VPI | 3.7a (1.4) | 3.8a,b (1.5) | 4.1a (1.8) | 4.4a,c (1.7) | 4.4b,c (1.7) | 4.2a,c (1.6) | 4.7c (1.8) |
Note. Means with the same subscript are not significantly different (p < .05). GMRC = Gates–MacGinitie Reading Tests Comprehension; TOWRE = Test of Word Reading Efficiency; WJIIINR = Woodcock–Johnson III Tests of Cognitive Abilities Numbers Reversed; SSRT = Stop Signal reaction time; SSINT = Stop Signal inattention; SSOE = Stop Signal omission errors; SSGRT = Stop Signal mean Go reaction time; SSRTV = Stop Signal reaction time variability; VPI = Verbal Proactive Interference.
a
n = 116.
b
n = 163; VPI n = 162.
c
n = 173.
d
n = 177.
e
n = 192; TOWRE and VPI n = 191.
f
n = 177; TOWRE n = 174, WJIIINR, n = 175, VPI n = 176.
g
n = 136.