Table 2.
Comparison of Admissions per 1000 Members for Propensity-Matched Control and Test Groups
| Period | Test group, N | Control group, N | Total population, by period, N |
|---|---|---|---|
| Time of first emergency department visit | 269 | 321 | 590 |
| Time of second emergency department visit | 664 | 555 | 1219 |
| Total population, by group | 933 | 876 | 1809 |
Chi-square test for independence: χ2 = 12.34; since P <.005, the admissions per 1000 members for each group and the 2 time periods are not independent.
Decrease in admissions per 1000 members for the test group between emergency department visits = 269 × (555/321) − 664 = (199).