Table 1.

Descriptive Statistics for all Measures Used in our Study.

	Kindergarten				Grade 2				Grade 4
	M (SD)	Range	Skew.	Kurt.	M (SD)	Range	Skew.	Kurt.	M (SD)	Range	Skew.	Kurt.
NO	14.66 (4.98)	0–26	-0.78	0.96	20.83 (2.84)	16–30	1.14	1.18	33.41 (3.21)	24–52	2.11	11.48
NO (lg)	1.14 (0.17)	0.67–1.41	-1.46	1.60	1.32 (0.06)	1.2–1.5	0.78	0.55	1.52 (0.03)	1.45–1.63	0.92	1.79
MPS	30.52 (5.65)	13–41	-0.53	0.19	42.35 (4.67)	31–58	0.08	0.71	50.61 (3.52)	42–65	1.16	3.55
TEMA	42.79 (13.02)	16–69	-0.03	-0.69	∖	∖	∖	∖	∖	∖	∖	∖
MF	∖	∖	∖	∖	67.21 (14.07)	39–98	0.15	-0.76	106.79 (16.96)	71–136	-0.01	-0.78
DE	0.78 (0.13)	0.38–0.96	-1.00	0.69	0.73 (0.10)	0.52–0.96	0.10	-0.23	0.77 (0.11)	0.38–0.96	-1.23	2.58
NLE	0.19 (0.09)	0.04–0.59	0.96	3.15	0.07 (0.03)	0.02–0.21	1.58	3.70	0.06 (0.03)	0.02–0.26	3.60	19.49
NLE(lg)	-0.77 (0.23)	-1.44–(-0.23)	-0.80	0.51	-1.20 (0.18)	-1.69–(-0.69)	0.20	0.19	-0.26 (0.17)	-1.75–(-0.59)	0.62	2.99
Intelligence	18.44 (6.15)	1–32	-0.66	0.76	25.12 (5.00)	14–37	0.19	-0.45	26.91 (5.89)	16–39	0.36	-0.73
Inhibition	0.64 (0.17)	0.03–1.09	-0.16	1.72	1.25 (0.47)	0.37–2.50	0.02	-0.49	0.74 (0.19)	0.08–1.31	-0.10	1.46
WM	6.75 (1.46)	4–9	-0.05	-1.07	8.00 (1.03)	5–9	-0.81	-0.23	8.23 (0.90)	6–9	-0.97	0.10

NO, numerical operations; MPS, math problem solving; TEMA, test of early mathematics ability; MF, math fluency; DE, dot estimation; NLE, number line estimation; Intelligence, nonverbal intelligence; WM, working memory.