Screening for speech and language delay: a systematic review of the literature.

Study selection Study designs of evaluations included in the review For intervention: the studies had to detail the number of participants in each group and the nature, duration, span, and delivery of treatment, provide a comparison of preand postintervention speech and language measures, and fulfill one of three design criteria: experimental study with randomised non-treatment controls; quasi-experimental studies (with non-random/pseudo-random or non-equivalent non-treatment control groups); or a single-subject experimental design with graphical displays or session-by-session data for individuals.