Cooke 2011.

Methods	Study design: Cluster‐randomised controlled trial Funding: "This research was supported by a grant from the Medical Research Council National Prevention Research Initiative."
Participants	Description:  422 children in reception (4 to 5 years) and Year 1 (5 to 6 years) from 16 classes in 8 schools. N (Randomised): 16 classes, 472 children % Female: 47% female Age: Reception: 4 to 5 years (N = 216) Year 1: 5 to 6 years (N = 206) SES and ethnicity:              “To ensure adequate representation of children from families of low socioeconomic status, we selected schools in which the proportions of pupils who were eligible for free school meals, who spoke English as a second language, and who came from minority ethnic backgrounds were above the national average." No individual child data on these variables were reported. Inclusion/exclusion criteria:      Not stated Recruitment: Recruited from 16 classes in 8 schools (492 children, 472 consented) Recruitment rate: Children: 96% (472/492) Schools: unknown Region: United Kingdom
Interventions	Number of experimental conditions: 4 Number of participants (analysed): Exposure + tangible non‐food reward (sticker) = 99 Exposure + social reward (praise) = 106 Exposure alone = 105 Control = 112 Description of interventions: “Children in the intervention conditions (ETR, EP, EA)* were seen individually from Day 3 to Day 14 and offered a small piece of their target vegetable.” Exposure + tangible non‐food reward: “Children in the ETR condition were told that if they tasted the vegetable, they could choose a sticker as a reward.” Exposure + social reward: “Children in the EP condition were praised if they tasted the vegetable (e.g. “Brilliant, you're a great taster”) Exposure alone: “Children in the EA condition were invited to taste the target vegetable but received minimal social interaction.” Duration: 3 weeks Number of contacts: 12 exposure sessions Setting: School Modality: Face‐to‐face, exposure Interventionist: Trained researchers Integrity: “Children in the three intervention groups agreed to taste their target vegetable in most sessions" Exposure + tangible non‐food reward (sticker): M = 11.34 sessions, SD = 1.45 Exposure + social reward (praise): M = 10.45 sessions, SD = 1.94; Exposure alone: M = 9.97 sessions,SD = 2.87. “Post hoc analyses showed higher compliance in the ETR condition than in the EP or EA conditions (p < 0.05), and compliance in the latter two conditions did not differ.” Date of study: Unknown Description of control: No‐treatment control: “Children in the control group did not receive taste exposure to the target vegetable during the intervention period.”
Outcomes	Outcome relating to children's fruit and vegetable consumption: As‐desired consumption of target vegetable (grams). “The child was then invited to eat as much of the vegetable as he or she wanted, with intake (in grams) assessed by weighing the dish before and after consumption using a digital scale” (NB. “Care was taken to ensure that children in the ETR condition understood that the sticker reward was no longer available.”) Length of follow‐up from baseline: Acquisition data: day 15 Maintenance data: 1 month and 3 months later Subgroup analyses: None Loss to follow‐up (at 1 month and 3 months follow‐up): Exposure + tangible non‐food reward (sticker): 7%, 9% Exposure + social reward (praise): 8%, 5% Exposure alone: 8%, 8% Control: 11%, 6% Analysis: Analysis adjusted for clustering“Clustering by school was minimal; therefore, the final analyses adjusted only for clustering by class." Sample size calculation was performed "On the basis of evidence that 10 exposures are needed to alter preferences, we decided to repeat all analyses for a restricted subset of children who tasted their target vegetable on at least 10 days (n=365). Because there were no significant differences between the restricted and the full samples, results are reported for the full sample."
Notes	Sensitivity analysis ‐ primary outcome: Primary outcome not stated, fruit and vegetable intake 2nd listed outcome after liking
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Contact with the author indicated that the study used blocked randomisation performed using an online randomiser programme
Allocation concealment (selection bias)	Unclear risk	Randomisation occurred prior to consent. Head teachers were not aware of group allocation. It is unclear if study personnel knew of allocation.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Contact with the author indicated that personnel were not blind to group allocations and that there was the potential that participants became aware of group allocation. However, given the objective outcome measure, review authors judged that the outcome would not be influenced by lack of blinding
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Contact with the author indicated that some, but not all of the outcome assessors were blind to group allocation. The outcome measurement (grams of target vegetable consumed, as measured by a digital scale) was objective and unlikely to have been influenced by lack of blinding
Incomplete outcome data (attrition bias) All outcomes	Low risk	Although reasons for missing data were not provided by group, rates of loss to follow‐up were low and similar across all experimental arms of the trial at both follow‐up points (Exposure+sticker = 6.5%, 8.8%; Exposure+praise = 8.2%, 5.0%; Exposure alone = 8.2%, 8.2%; Control = 10.9%, 5.7%, provided by the author). No reasons were reported for loss to follow‐up
Selective reporting (reporting bias)	Unclear risk	Insufficient information to permit judgement Trial was registered, but not prospectively (ISRCTN42922680)
Other bias	Low risk	No further risks of bias identified