Sirbu 1978.

Methods	Parallel randomised controlled trial.
Participants	Participants: volunteer mothers of preschool children. Sex: all mothers. Age of parents: not stated. Unit of allocation: individual participant. Number randomised: 60 (number randomised to the four conditions; no further information). Number used in analysis: number available in analysis not stated*. Country & setting: USA; single‐site; recruited from community settings; intervention delivered in the community. Inclusion criteria: mothers of preschool children. Exclusion criteria: not stated. Ethnicity: all Caucasian. Baseline characteristics: no significant differences between the four conditions in the mother's level of education, occupation, number of children, or significant medical problems.
Interventions	Four conditions: three behavioural parenting training groups (course & programmed text; course alone; programmed text alone); attention‐placebo control. Duration of intervention: 5 weeks. Length of follow‐up: none.
Outcomes	Stress (Parent Stress Satisfaction Questionnaire)*.
Notes	*Insufficient data to calculate effect sizes. Clarification was requested from the trial investigators but no further information was available at the time this review was prepared.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Trial investigators report that mothers "were randomly assigned to one of four treatment groups" (page164). Information reported insufficient for a judgement to be made. We requested clarification from the trial investigators, but no further information was available at the time this review was prepared.
Allocation concealment (selection bias)	Unclear risk	Information reported insufficient for a judgement to be made. We requested clarification from the trial investigators, but no further information was available at the time this review was prepared.
Blinding (performance bias and detection bias) Participants	High risk	Trial investigators report that "instructions were given to each groups about the course, and in the case of Groups 2 and 4, not to look at a copy of Becker's book" (page 165), thus attempting to ensure participants were unaware of the type of intervention they were receiving. However, there is no information whether the instructions given were followed.
Blinding (performance bias and detection bias) Personnel	Unclear risk	Information reported insufficient for a judgement to be made. We requested clarification from the trial investigators, but no further information was available at the time this review was prepared.
Blinding (performance bias and detection bias) Outcome assessors	Unclear risk	Information reported insufficient for a judgement to be made. We requested clarification from the trial investigators, but no further information was available at the time this review was prepared.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Information reported insufficient for a judgement to be made. We requested clarification from the trial investigators, but no further information was available at the time this review was prepared.
Selective reporting (reporting bias)	Low risk	Review authors judge that the published report includes all expected outcomes, including those that were pre‐specified.
Other bias	Low risk	The study appears to be free of other sources of bias.