TABLE 1.

Sampling framework for substance abuse treatment programs serving American Indian and Alaska native communities.

Strata	Sub-strata	Participation rate (%)
I. Large tribes (20 largest, by population on reservation or service area [e.g., Oklahoma])	None	40
II. Urban Indian health clinics (36 members of NCUIH)	None	67
III. Alaska native health corporations (21 formed as part of Alaska Tribal Health Compact)	None	79
IV. Other tribes (federally recognized minus the 20 largest). Because of the large number of tribes (317) and the likely data collection challenges, tribes were selected in replicates of 50 with proportional weighting of tribes by region	Four geographic regions: (1) Pacific Coast; (2) Intermountain West and Southern/Central Plains; (3) Northern Plains, Midwest, and Northeast; and (4) Southeast and Mid-Atlantic	64
V. Other local and regional programs (independent nonprofit or for profit)	None	50

Notes: NCUIH ¼ National Center for Urban Indian Health. Overall participation rate was 63%.