Table 6. Bivariate Probit Estimates Probability-of-Use Equations from Two-Part Model Parameter Estimates and Standard Errors.
| Instrument | Bivariate Probit Estimates | Two-Stage Least Squares Estimates | ||||||
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| Coefficient of QMB Enrollment | Average Treatment Effect | Coefficient of QMB Enrollment | Specification Test Statistic | |||||
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| Standard Mean | Deviation | Standard Mean | Deviation | Standard Mean | Standard Deviation | Mean | Deviation | |
| Any Part B Charges (Estimates from Table 3)1 | 0.474 | 0.092 | 0.125 | 0.023 | — | — | — | — |
| Percent of Medicaid Population That Is Elderly | 0.492 | 0.545 | 0.129 | 0.139 | 0.268 | 0.175 | — | — |
| Percent of Medicaid Population That Is Elderly, and Its Square | 0.516 | 0.391 | 0.135 | 0.100 | 0.196 | 0.128 | 0.37 | — |
| Percent of Medicaid Population That Is Elderly and Number of QMB Outreach Programs 0-7 | 0.579 | 0.484 | 0.152 | 0.123 | 0.257 | 0.151 | 0.02 | — |
| Any Part A Charges (Estimates from Table 3)1 | 0.292 | 0.090 | 0.079 | 0.025 | — | — | — | — |
| Percent of Medicaid Population That Is Elderly | -0.113 | 0.518 | -0.030 | 0.138 | -0.059 | 0.172 | — | — |
| Percent of Medicaid Population That Is Elderly, and Its Square | 0.034 | 0.407 | 0.010 | 0.109 | 0.056 | 0.126 | 1.02 | — |
| Percent of Medicaid Population That Is Elderly and Number of QMB Outreach Programs 0-7 | 0.106 | 0.488 | 0.029 | 0.131 | 0.080 | 0.147 | 2.68 | — |
1
Estimates in Table 3 are the single-equation probit estimates that assume that QMB enrollment is not a function of anticipated medical care use.
NOTES: Other exogenous variables include those listed in Table 3. QMB is qualified Medicare beneficiary.
SOURCE: Parente, S., and Evans, W., Project HOPE, Bethesda, MD, 1999.