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Table 1 Examples of Generalizability Biases in the Childhood Obesity Literature

From: Identification and evaluation of risk of generalizability biases in pilot versus efficacy/effectiveness trials: a systematic review and meta-analysis

Bias Likely Larger Effect Likely Smaller/No Effect
Study Fitzgibbon 2005 [25] Kong 2016 [26]
 Who delivered the intervention? “…the use of specially trained early childhood educators rather than classroom teachers to deliver the intervention, thereby raising questions of generalizability.” “…using teachers in existing Head Start classrooms to deliver the intervention.”
Study Cohen 2015 [27] Sutherland 2017 [28]
 How much of the intervention was provided? 1 full day training and 1 half day training 1 90-min training
Study Beets 2016 [29] Beets 2018 [30]
 How much support to implement the intervention was provided? “During the first year of receiving the intervention for both the immediate and delayed program, each program received four booster sessions. During the second year of receiving the intervention (for the immediate condition only) 2 booster sessions/program were provided.” No additional onsite booster sessions or follow-up
Study Sutherland 2016 [31]  
 Who delivered the intervention? “The provision of an in-school physical activity consultant for 1 day per week was the largest cost relating to the efficacy trial (66% of the total intervention cost). Whilst the provision of an in-school physical activity consultant was necessary under efficacy trial conditions in order to evaluate the effect of the combination of intervention strategies, the feasibility of providing a part-time consultant within schools across large geographic regions and the cost of such a model of support presents challenges in upscaling the intervention. The dissemination of an effective intervention across the community requires the use of implementation strategies which better mirror real world practice.”  
Study McKenzie 1996 [32] Hoelscher 2004 [33] (PE outcomes)
 How much support to implement the intervention was provided? “Following initial training, CATCH PE consultants provided on-site follow-up approximately every 2 weeks. During the 2.5 years, consultants made 3089 documented school visits, averaging 55.3 per school and 51.7 min in length. Consultants performed various roles during visits, including giving feedback to teachers, modeling new lesson segments, team teaching, and providing motivation and technical support.” No onsite, on-going support provided
Study Salmon 2008 [34] Salmon 2011 [37]
 How much of the intervention was provided? 19 lessons delivered 6 lessons delivered
“…Switch-2-Activity involved an abbreviated programme; therefore, the intervention ‘dose’ was lower…”
 How long was the intervention delivered? 10 months 7 weeks
 Who delivered the intervention? “All intervention components were delivered by one intervention specialist (a qualified Physical Education teacher) across all three schools.” “the programme was delivered by regular class teachers rather than by a specialist university research team…”
 What measures were used to collect information on outcomes? Objective measures Self-report
Study West 2010 [35] Gerards 2015 [36]
 Who delivered the intervention? “All sessions were facilitated by a clinical psychologist and accredited provider of the intervention (who co-authored the intervention materials), with assistance from graduate students in nutrition and dietetics, physical education, and psychology.” “The intervention was led by three different facilitators. These health professionals have been accredited after attending an official 3-day training course and an additional intervention day.”
“Finally, the West 2010 [35] study was implemented as an efficacy study, while in the current trial we tried to implement in the real life situation, which may have led to less significant study results.”
 Who received the intervention? “participants were mainly white, well-educated parents with moderate levels of employment and income.”