Justification of sample size
The primary aim of this study is to compare the intervention effect of TRUE HAVEN versus control on average yearly shooting victim rates. With an average of 10,295 residents per neighborhood per year, leading to approximately 432,390 person-steps of follow-up over 3.5 years, for a two-sided test between Poisson rates with a Type I error of 0.05, intra-cluster correlation coefficient (ICC) of 0.50 as currently estimated in these 6 neighborhoods of New Haven, and a baseline shooting rate of 6 shooting victims per 10,000 persons per step in the control period as currently observed on average in these New Haven neighborhoods, our study will have about 80% power to detect a 28% decrease or greater in the primary outcome, average neighborhood shooting rates, in relation to the full TRUE HAVEN intervention package [For individual-level outcomes of the housing assistance component, with approximately 1400 total participants (i.e., 233 participant individuals/families per neighborhood group) enrolled during the 3.5 year study period, that is, about 33 participants per neighborhood per 0.5 year step, for binary outcomes (e.g., % homeownership, % housing costs < 30% of income, % improved credit score), for a two-sided test of the difference between proportions with a Type 1 error of 0.05, with ICCs as low as 0.01 and as high as 0.2, our study will achieve at least 80% power to detect an increase with the TRUE HAVEN intervention of at least 2.4% points for outcomes where the baseline proportion is 1% or less, 10% points for outcomes where the baseline proportion is 20% or less, and 12% points for outcomes where the baseline proportion is 40% or less.