International Journal of Drug Policy - 2014

Volume 25 Issue 3 May 2014

Issue link:

Contents of this Issue


Page 19 of 153

520 A.N. Martinez et al. / International Journal of Drug Policy 25 (2014) 516–524 Fig. 2. Routes that link locations of sleeping, hanging out and using drugs (N = 989). Census tract of residence was assessed using intraclass correlations (Hedeker, Gibbons, & Flay, 1994; Larsen & Merlo, 2005; Wright, Bobashev, & Novak, 2005). Our sampling methods did not include nesting of participants within Census tracts so it was unclear whether autocorrelation of respondents would violate the assump- tion of independence for ordinary least squares regression analyses and increase type I error rates. Intra-class correlations computed in SPSS showed that variability at the census tract level was not independent of variability at the individual level. Therefore we did not utilize multilevel logistic models with random intercepts to measure between group variations in the outcome as a percentage of total variation in the outcome (which is comprised of within- and between-group variance). Rather, all multivariate analyses were conducted using ordinary least squares regression in SPSS Version 20.0, IBM, New York). Thematic mapping ArcGIS software was used to create all thematic maps (ESRI, Redlands, CA). All street-based network and census tract shape- files were accessed from the publicly available GIS enterprise data clearinghouse operated by the City and County of San Francisco. The purpose of thematic mapping is to visualize the distribution of activity space routes across the city of San Francisco.

Articles in this issue

view archives of International Journal of Drug Policy - 2014 - Volume 25 Issue 3 May 2014