Table 5. Regression of the log case-mix index in a hospital quarter minus the log case-mix index for the same hospital in the first quarter of calendar year 1981.
| Variable | Coefficient | Standard error | Significance level |
|---|---|---|---|
| April-June 1983 indicator | 0.0039 | 0.0022 | 0.08 |
| July-September 1983 indicator | 0.0084 | 0.0022 | 0.0002 |
| Fiscal year 1984 indicator | 0.0111 | 0.0023 | 0.0001 |
| On prospective payment system during quarter | 0.0149 | 0.0020 | 0.0001 |
| Number of quarters on prospective payment system | 0.0022 | 0.0018 | 0.03 |
| Trend for base case | 0.0105 | 0.0010 | 0.0001 |
| Trend by teaching status | — | — | 0.0001 |
| No teaching | −0.0025 | 0.0011 | — |
| Minor teaching | −0.0042 | 0.0011 | — |
| Major teaching | 0.0000 | c.g. | — |
| Trend by 500 or more beds | 0.0053 | 0.0006 | 0.0001 |
| Trend by urban location | −0.0001 | 0.0005 | n.s. |
| Trend by division | — | — | 0.0001 |
| New England | −0.0117 | 0.0019 | — |
| Mid-Atlantic | −0.0047 | 0.0027 | — |
| South Atlantic | −0.0022 | 0.0015 | — |
| East North Central | −0.0068 | 0.0013 | — |
| East South Central | −0.0121 | 0.0026 | — |
| West North Central | −0.0002 | 0.0018 | — |
| West South Central | 0.0001 | 0.0025 | — |
| Mountain | 0.0036 | 0.0021 | — |
| Pacific | 0.0000 | c.g. | — |
NOTE: Based on 9,869 hospital quarters, R2 = 0.152; c.g. = comparison group; n.s. = not significant. The regression also contains 36 coefficients for the four seasons in each of the 9 census divisions. These results are available from the authors.
SOURCE: The Rand Corporation: Analysis of data from the Professional Activity Study.