Griffith 2012.

Methods	Design: Randomised controlled trial Unit of randomisation: Parent/child dyads Follow‐up: 6 months Study dates: October 2007 to September 2010
Participants	Participants: Parents (87 mothers, 2 fathers) living in a designated Flying Start area (low socioeconomic area) Mean age of parents: 28.97 (SD 6.72; range: NR) years; intervention group: 28.6 (SD 7.0; range: NR) years, control group: 29.8 (SD 6.1; range: NR) years Age of child: 21.2 (SD 6.3, range 12 to 36) months; 37 girls and 52 boys Ethnicity: Not reported Number randomised: 89 (intervention 60; control 29) Country & setting: UK (Wales); multi‐site; recruited from Flying Start centres; delivery of intervention not reported Eligibility criteria: Child aged 12 to 36 months; parent and child must live within a designated Flying Start area in Wales; and families not to have been on an Incredible Years parenting programme in the past
Interventions	Two conditions: Group parent training (Incredible Years Toddler parenting programme); wait‐list control Duration of intervention: 12 (2.5 hours) sessions over 12 weeks Therapist training: Trained group leaders with mentor’s supervision
Outcomes	Secondary outcomes: Parent‐child interaction as measured by the Dyadic Parent‐Child Interaction Scale, reported by observing researcher Timing of outcomes: Outcomes reported for 6 months follow‐up Primary outcomes/adverse events: No other outcomes relevant to this review specified
Notes	Level of prevention: Primary Funding: the Welsh Assembly Government, Welsh Language Board, and Incredible Years Cymru
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The study reported that participants were randomised using a "remote dynamic randomisation service provided by an independent trials unit"
Allocation concealment (selection bias)	Low risk	The study reported that participants were randomised using a "remote dynamic randomisation service provided by an independent trials unit"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants: It would not have been possible to fully blind participants in this type of study (there is an obvious difference between receiving group training and being placed on a waiting list). No indication of any specific additional measures taken to reduce the risk of bias that might result from differential behaviours by participants were found Personnel: The design of the study meant that personnel delivering the intervention were aware which groups had been assigned to the different study conditions
Blinding of outcome assessment (detection bias) Independent observer reported outcomes	Low risk	The investigators reported that observers were blinded to the participants' experimental condition at baseline and follow‐up
Blinding of outcome assessment (detection bias) Parent reported outcomes	Low risk	There were no parent‐reported outcomes
Incomplete outcome data (attrition bias) All outcomes	Low risk	100% of participants completed the Schedule of Growing Skills assessment at follow‐up. 44/60 (73%) of the intervention group and 23/29 (79%) of the control group completed the Dyadic Parent‐Child Interaction Scale at follow‐up
Selective reporting (reporting bias)	Low risk	The published report included all expected outcomes, including those that were prespecified
Other bias	Low risk	The study appeared to be free of other sources of bias