Data analysis
REGRESSION, SECONDARY
Descriptive characteristics of nursing home residents included variables assessed as part of the RAI assessment: therefore, only those residents for whom a recent RAI assessment had been completed were included in the analysis of resident characteristics at baseline. Primary outcome analyses included the broader population of included physicians’ residents. All primary analyses were by intention-to-treat and compared the four arms. The primary outcome was analyzed using a general linear mixed effects regression model; time was specified as a continuous variable, and a common secular trend was imposed across all study arms with the effect of the intervention modelled as a slope deviation from the trend. The analysis adjusted for the size of each home (number of beds) as a fixed effect. A random intercept and slope for time were specified for the unit of randomization (group of homes). The primary comparison between the arms at 6 months post-intervention was estimated using least square mean differences, together with 95% confidence intervals. Factorial analyses were conducted as a secondary analysis because the traditional approach (i.e., an interaction test followed by dropping the interaction term if non-significant) can lead to bias in factorial trials [