Table 1.

Descriptive statistics of model variables and indicators.

Variable	N before imputation	(imputed) N	M	SD
Age of independent walking	30	31	15.24	2.34
Exploration through self-locomotion 20 months	28	30	0.46	0.19
Total score productive spatial language 43 monthsa	30	31	-0.08	0.94
Spatial verbs productive 43 months	-	30	10.63	3.34
Spatial prepositions productive 43 months	-	28	5.83	2.14
Receptive vocabulary 43 monthsb	31	31	56.32	10.05
Total score grammatical and lexical categories 43 monthsa	28	31	0.09	0.94
Determiner omission 43 months	-	28	16.57	5.09
Subject omission 43 months	-	28	9.04	2.70
Auxiliary omission 43 months	-	28	9.89	2.62
Verbal prefix omission 43 months	-	28	11.00	1.19

Missing values were imputed at the level of total scores, therefore the total scores presented are after imputation but the raw scores still contain all missing values. ^aThis score is a mean of Z scores ^bRaw scores of the PPVT-III were used in the analysis.