Bignall 2015.

Methods	Included as process evaluation Intervention study design: randomised controlled trial Unit of allocation: child Process evaluation methods: descriptive/bivariate (quantitative), descriptive (qualitative)
Participants	Setting: single high school in a midwestern city in the USA Age of children: 12 to 17 years (mean age, 15.47 years) Child characteristics (BME/SES): African American Asthma status: asthmatic only Intervention recipients: children
Interventions	School type: high school Intervention description: 2 short instructional sessions for children on relaxation/breathing retraining techniques. Participants completed 2 in‐person visits spaced 1 month apart and were given a copy of the script and a CD with breathing retraining techniques to help them practise at home Control description: participants in the control group received 30 minutes of standard asthma education Theoretical framework: no specific framework was named (although supporting literature around breathing exercises was provided)
Outcomes	Core processes evaluated (child level): attrition, dosage, adherence
Notes	Process evaluation category: named section(s) on processes included Breadth and depth: neither broad nor deep Voice of children given prominence: featured but not sufficiently Note: not included as outcome evaluation because control received asthma education Funding source: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	N/A
Allocation concealment (selection bias)	Unclear risk	N/A
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	N/A
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	N/A
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	N/A
Selective reporting (reporting bias)	Unclear risk	N/A
Other bias	Unclear risk	N/A
Transparent and clearly stated aims	Low risk	Study aims were clearly stated
Explicit theories underpinning and/or literature review	High risk	No named theoretical framework was presented
Transparent and clearly stated methods and tools	Unclear risk	Although methods and tools were clearly described, it is unclear who delivered the intervention. However, tools used and the content of interviews were well described
Selective reporting	Unclear risk	Interviews may have been underreported
Harmful effects	High risk	Not much scope for harmful effects, such as impact of disruption of the intervention, to be studied
Population and sample described well	Low risk	The most relevant characteristics of the sample were captured
Continuous evaluation	Low risk	Data were collected before and after the intervention
Evaluation participation equity and sampling	High risk	Only child‐level data were collected
Design and methods overall approach	Low risk	Two sets of data were provided
Tools and methods of data collection reliable/credible	Unclear risk	Difficult to establish whether these were reliable, as they were interviews
Tools and methods of data analysis reliable/credible	Unclear risk	Analysis of quantitative data was comprehensive. However, treatment/analysis of qualitative data was unclear
Performance bias/neutrality/credibility/conformability	High risk	Because of the way in which qualitative interviews were conducted, risk of performance bias was increased
Reliability of findings and recommendations	High risk	Study included a small sample, and target numbers for the study were not achieved. Presentation of qualitative data was limited
Transferability of findings	High risk	Study authors did consider transferability of findings; however analysis of qualitative data was absent
Overall risk of bias of process evaluation	High risk	Some data were collected well; however treatment of qualitative data reveals high risk of bias