Sample Size Considerations
RECRUITMENT
This study had a fixed number of 12 clusters by design. Mental health service delivery organizations participated based on their commitment to implementing iCBT services. For service providers, the sample size needed for sufficient power to test the use of the ItFits-toolkit on the degree of normalization (ie, NoMAD) was obtained from a power analysis using simulated data. As there was no prior knowledge concerning the NoMAD in detecting changes in normalization, we assumed a 5% increase in absolute normalization scores and an increase in the 3-month growth rate from 0.05 to 0.10. A cluster sample size of 15 service providers for each of the 12 mental health organizations per wave was estimated to be sufficient to achieve 80% power to detect the effect using a 2-sided test with a significance level α of .05. The first 2 data collection waves were used to obtain a stable sample, and recruitment was closed in wave 3. Replacements were sought for those service providers who had dropped out of the study.