Fig 1.
Schedule of enrolment and assessments.
*Because of recruitment taking place in a variety of non-research settings, a relatively short questionnaire needs to be completed at enrolment, and a follow-up questionnaire with additional questions will be sent to the participants by email (cfr. PART II).
Table 1.
The minimum sample size for comparing two proportions assuming a two-sided significance level of 95%, a power of 80% and a ratio of sample sizes of three.
Fig 2.
Sampling scheme for the selection of clusters in which each cluster is represented by a segment proportional to its expected number of attendees with k the sampling interval, p the number of subjects per sample group and n the required sample size.
The sum of the segments represents the total population (N).