Design and materials
cough
Materials were 64 vignettes depicting children with cough (see Supplementary Table S1). Each child was described in terms of the STARWAVe factors, which were manipulated in a half-fractional factorial design (Manipulation of STARWAVe factors in the present study


The vignettes were divided into two sets (set A and B) and each set was subdivided into two surveys. GPs were randomly assigned to either set A or B and saw the two surveys 24 h apart (order counterbalanced across GPs). The number of very-low, normal, and high-risk cases was consistent across sets and surveys (see Supplementary Table S2).Seven ‘parental concern’ vignettes were also constructed, by adding the phrase ‘the parent is quite concerned’ to each of the seven very-low-risk cases (see Supplementary Table S3). Each GP saw one parental concern vignette, selected at random from the very-low-risk cases in their unseen set. This vignette was always presented last, so as not to influence responses to the ‘primary’ vignettes.