Table 4 Efficacy assessment composite metrics computed from the three pre- and post-treatment language samples collected by the parent

Youth total number of story-related utterances

The total number of child utterances directly related to the semantic or conceptual content of the story. Repetitions and completely unintelligible utterances were not included. This metric provides an index of the total amount of child talk.

Youth number of different word roots (NDWR)

The NDWR in the first 50 story-related utterances or in the child’s total number of story-related utterances if the child produced less than 50 story-related utterances. This metric provides an index of child vocabulary size.

Parent total number of story-related utterances

The total number of story-related parent utterances. This metric includes parent’s use of the specific strategies taught in the intervention (i.e., recasts, WH-questions, and fill-in-the-blank prompts) and provides an index of the total amount of parent talk.