Sample size {14}
cluster loss
EVENT
Due to the complexity of the study design with respect to power estimation, a sample size calculation was performed via simulation using SAS 9.4. Resident-level baseline and treatment profiles were generated according to best estimates of care event counts and skin health behaviours. Cluster-wide effects were added to the simulated responses such that an intra-cluster correlation (ICC) of 25% in both co-primary endpoints was present. Plausible values for the ICC were considered based on published results in Lee A simulation set of 1000 hypothetical studies, with cluster sizes varying at random between 3 and 9 residents uniformly, was generated. Assuming an average decrease (i.e. improved efficiency) in the care efficiency score of 20% (σσ = 7.3%) as compared to usual care and an average reduction (i.e. improved skin health) of 0.2 (σσ = 0.3) in skin health grade as compared to usual care, a sample size of 16 clusters in total yields a power of 86.4%. To allow for cluster loss and to maintain a balanced study design, 20 clusters will be recruited, 10 in Canada and 10 in Germany. Based on the average site capacity, these 20 clusters correspond to approximately 180 individual residents. Caregivers will be recruited from the participating care units; we anticipate having at least 8 caregivers per cluster being able to contribute to the study or 160 caregivers in total.