Table 15. Independent Variables Used in the Regression Analyses: Mean Value in U.S. Census Region and Range in PSRO Areas.

Variable	Mean	Standard Deviation	Highest PSRO area	Lowest PSRO area	Variable	Mean	Standard Deviation	Highest PSRO area	Lowest PSRO area
Age (Medicare enrollees: percent 75 years and over)					Short-stay beds (per 1,000 Medicare enrollees)
Northeast	41.3	1.8	46.7	36.9	Northeast	40.1	7.6	61.2	24.7
North Central	41.9	2.1	45.6	36.6	North Central	48.5	6.7	64.0	32.3
South	39.1	2.3	44.4	33.0	South	45.7	12.8	79.4	17.8
West	40.3	2.9	45.1	31.1	West	41.6	23.3	164.0	26.2
Sex (Medicare enrollees: percent female)					Occupancy in short-stay hospitals (percent)
Northeast	60.9	1.2	63.2	57.9	Northeast	80.8	4.7	88.3	68.6
North Central	59.7	1.6	62.6	54.9	North Central	73.7	5.2	82.4	60.9
South	59.2	2.3	64.1	53.2	South	72.4	4.7	85.5	65.5
West	58.2	3.1	62.3	48.4	West	67.0	4.6	75.6	54.5
Race (Medicare enrollees: percent non-white)					Physicians (per 1,000 Medicare enrollees)
Northeast	5.5	5.2	22.3	.3	Northeast	15.5	5.0	27.4	6.8
North Central	5.3	4.5	23.4	.2	North Central	12.1	4.4	24.8	5.0
South	14.2	11.0	51.8	2.6	South	12.1	8.8	49.3	4.8
West	6.8	12.1	70.9	.6	West	17.4	6.6	41.5	10.0
Density (Percent of total population living in SMSAs)					Nursing home beds (per 1,000 Medicare enrollees)
Northeast	84.4	29.2	100.0	.0	Northeast	40.7	17.7	84.0	8.8
North Central	70.3	29.3	100.0	.0	North Central	57.3	17.4	106.2	19.2
South	64.4	29.4	100.0	.0	South	40.8	17.6	85.1	9.4
West	80.8	32.9	100.0	.0	West	49.9	17.8	105.0	12.3

Source: Medicare Statistical System: Age, Sex, Race, (1979)

Area Resource File: Short-stay beds, physicians, and occupancy, (1978); Density, (1977); Nursing home beds, (1976)