Bradley 2003.

Methods	Design: Randomised controlled trial Unit of randomisation: Individual caregiver Follow‐up: 3 months Study dates: 1998 to 1999
Participants	Participants: Parents (gender not reported) who were experiencing problems managing the behaviour of their children Mean age of child: Intervention 3.76 (SD 0.66), control 3.84 (SD 0.57) Mean age of parent: Intervention 35.20 (SD 5.51), control 35.88 (SD 5.73) Ethnicity: Not reported Number randomised: 198 (intervention 89, control 109) Country & setting: Canada; single‐site; recruited from community settings; intervention delivered in community agencies Eligibility criteria: Not specified
Interventions	2 conditions: Group‐based parent training (1‐2‐3 Magic); wait‐list control Duration of intervention: 3 (2 hours) sessions in 3 weeks + 1 booster 4 weeks after completion of the intervention Therapist training: Facilitators trained in problem solving
Outcomes	Externalising problems subscale ‐ hyperactivity/inattention: Preschool Behaviour Questionnaire ‐ hyper/distractible, as completed by parents (total score and persistent/unstoppable subscale data not added) Internalising problems: Preschool Characteristics Questionnaire ‐ negative adaptation and affect, as completed by parents (difficulties subscale data not added) Timing of outcomes: Outcomes reported for 3 months follow‐up Secondary outcomes/adverse events: No other outcomes relevant to this review specified
Notes	Level of prevention: Secondary/tertiary Funding: The Counselling Foundation of Canada
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The study reported that participants were randomly assigned, but no further details were reported for a judgement to be made. We requested clarification from study investigators, but no further information was available at the time this review was prepared
Allocation concealment (selection bias)	Unclear risk	Information reported insufficiently for a judgement to be made. We requested clarification from study investigators, but no further information was available at the time this review was prepared
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 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 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	There were no independent observer‐rated outcomes
Blinding of outcome assessment (detection bias) Parent reported outcomes	High risk	Outcome assessments by parents were not blinded as parents were aware of the intervention condition
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	8/89 (9%) of intervention group members and 16/109 (15%) of control group members did not complete post‐test assessments. Reasons for dropping out were not reported. The study reports that intention‐to‐treat analysis was planned, but it seems only completers were analysed
Selective reporting (reporting bias)	High risk	The published report included all expected outcomes, including those that were prespecified. However, only statistically significant results were fully reported for the Preschool Behaviour Questionnaire scales (hostile/aggressive and anxious subscales were not reported)
Other bias	Low risk	The study appeared to be free of other sources of bias