Table 2. Process evaluation and treatment fidelity strategies for the intervention.

Category	Goal / Description	Strategies
Monitor and improve provider training	Ensure provider skill acquisition	The first author had delivered a similar intervention protocol in three previous studies with the third authora. Before delivering the intervention, the first and third authors met to plan the intervention strategies. This was done using standardised protocols/checklists implemented in the pilot studies.
Monitor and improve treatment delivery	Ensure the treatments are being delivered/ adhered to in the way in which they were conceived with regard to content and treatment dose.	Parents. Parents received individual training in week 1 involving a demonstration of the home resource that included: a DVD, manual and play cardsb. During parent-training, the following dimensions were covered: providing feedback before, after and during play-dates, helping children resolve conflicts and strategies that promote social interactions. Treatment fidelity was monitored by the therapist recording parent reported treatment adherence weekly.
		Therapist. During the intervention, the first and third author met weekly to review video footage and to discuss the first author’s use of techniques. Three occupational therapy students were trained as clinic assistants to ensure uniformity in the treatment delivery. The students were present across all phases of the intervention for 47% of the 319 sessions. Students ensured the clinic playroom was set up consistently for each session and observed the therapist’s adherence to protocols for: children’s video feedback, playroom interactions, parent-therapist discussions and the completion of checklists.
	Minimise contamination across treatment conditions	Only one session was conducted at a time in the clinic. Participants did not have contact with or the contact details of other participants in the program. Children’s medication status was maintained and parents did not to commence additional therapy during the waitlist/intervention.
Monitor and improve receipt of treatment	Ensure participant comprehension and ability to use target strategies	Children’s comprehension of strategies and content had been developed across three pilot studiesa. Parent training and ongoing consultation was used to ensure parents’ comprehension and use of material. Parents discussed home DVD content with their child to ensure children comprehended the key messages. Therapist-child discussions in video-feedback sessions ensured children understood self-modelling footage. In week 7, children first played without the therapist to allow the observation of target skills when support was withdrawn. A post-test measurement was taken in week 10.

Notes. Framework for process evaluation strategies adapted from: Bellg et al. [41], Borrelli et al. [42], Czajkowski [43] and Spillane et al. [40].

^a Wilkes-Gillan et al. [21, 32, 33].

^bThe Ultimate Guide to Making Friends [44].