Table 1. Study 1: Sample size, child age, and language measures at each data collection wave.
N represents the number of available observations. Except for wave 1 (child age in months), child ages are in years.
| Data collection wave | N | Child age, M (SD) | Measures | Scales | Source |
| 1 | 859 | 6.24 (0.45) | Modified DDST (53) | Communication | Caregiver |
| 2 | 873 | 1.28 (0.06) | Modified MCDI Words and Gestures (11) |
Understand, vocabulary, and social (nonverbal) communication |
Caregiver |
| 3 | 894 | 1.51 (0.04) | Modified DDST (53) | Communication | Caregiver |
| 4 | 862 | 2.01 (0.03) | Modified MCDI Words and Sentences (11) |
Vocabulary, grammar, plurals, and tense |
Caregiver |
| 5 | 857 | 2.07 (0.02) | RDLS (54) | Comprehension | Child assessment |
| 6 | 852 | 3.19 (0.09) | Modified MCDI Words and Sentences (11) |
Vocabulary, plurals, past tense, and word combination |
Caregiver |
| 7 | 788 | 4.07 (0.03) | WPPSI (41) | Information, comprehension, vocabulary, and similarity |
Child assessment |
| 8 | 756 | 5.15 (0.06) | Bus Story Test (55) | Information and sentence length |
Child assessment |
| RDLS (54) | Comprehension | Child assessment | |||
| Initial Consonant Detection Test (56) |
Number of correct responses |
Child assessment | |||
| 9 | 720 | 7.44 (0.12) | WORD (57) | Reading and spelling | Child assessment |
| Phoneme Detection Task (58) |
Number of correct responses |
Child assessment | |||
| 10 | 661 | 8.62 (0.18) | WISC (59) | Information, comprehension, vocabulary, and similarity |
Child assessment |
| WOLD (60) | Listening comprehension and oral expression |
Child assessment | |||
| 11 | 668 | 9.84 (0.17) | WORD (57) | Number of correct responses (real and nonreal words) |
Child assessment |
| NARA II (62) | Accuracy and comprehension |
Child assessment | |||
| 12 | 502 | 13.77 (0.15) | TOWRE (63) | Number of correct responses (word and pseudoword) |
Child assessment |
| 13 | 472 | 15.34 (0.16) | WASI (64) | Vocabulary | Child assessment |