Sample size {14}
Power analysis was conducted using software PASS.15 for the primary outcome (change in salivary cotinine over a year) in Aims 1 and 2. Sampling 16 clusters (buildings) with 4 subjects per cluster (smokers for Aim 1, non-smokers for Aim 2) in each arm, we have 128 subjects per group or 256 in groups with or without a specific type of treatment (e.g., resident endorsement vs. no endorsement, cessation vs. no cessation). We calculated effect size as group mean difference in unit of standard deviation (SD) of the outcome, based on a two-sided test for mean difference between two groups in a cluster-randomized design with power of 80%. To compare groups with and without specific type of treatment, the group size of 256 may detect effect size of 0.283SD, 0.299SD, and 0.312SD at significance level alpha=0.05 for intra-cluster correlation coefficient 