Statistical analysis
BLIND
An intent-to-treat (ITT) analysis with all carers who provided follow-up data was conducted by a statistician who was blind to group allocation, followed by a per-protocol (PP) analysis with carers who completed treatment. A hierarchical linear modelling approach was used in order to account for the nested structure of the data (The power analysis was based on assumptions that the average unit comprised 1.5 carers, the intraclass correlation coefficient within units was 0.2, the correlation within rounds was 0.03 and that each round would comprise 9.4 carers. Using these parameters, the maximum design effect was 1.24. Assuming a 0.5 correlation between baseline and outcome measures, a total sample of 54 units was deemed to have 80% power to detect a difference of 0.5 standard deviations (medium size difference) between the arms.