Table III.
Bias and Nominal 95% Confidence Interval Coverage rates of treatment effect estimation using 6 DD models
| Setting | Bias | |||||
|---|---|---|---|---|---|---|
| (1): Naïve DD |
(2): DD with X |
(3): (1) with separate wts |
(4): (2) with separate wts |
(5): (1) with 4 group weighting |
(6): (2) with 4 group weighting |
|
| 1 | −0.0047 | −0.0048 | −0.0047 | −0.0047 | −0.0048 | −0.0048 |
| 2 | 0.060 | 0.060 | −0.023 | −0.023 | −0.00043 | −0.00064 |
| 3 | 0.112 | 0.111 | 0.029 | 0.029 | 0.0017 | 0.0018 |
| 4 | 0.204 | 0.089 | −0.034 | −0.035 | 0.00026 | 0.00024 |
|
Confidence interval coverage (Nominal=.95) |
||||||
|
(1): Naïve DD |
(2): DD with X |
(3): (1) with separate wts |
(4): (2) with separate wts |
(5): (1) with 4 group weighting |
(6): (2) with 4 group weighting |
|
| 1 | .94 | .95 | .97 | .95 | .96 | .95 |
| 2 | .91 | .90 | .96 | .94 | .96 | .94 |
| 3 | .79 | .76 | .95 | .93 | .96 | .95 |
| 4 | .44 | .83 | .94 | .92 | .95 | .93 |