Table 1.
Covariate | Levels | Nested nominal covariate,
νk k = 1, …, 6 |
|||||
---|---|---|---|---|---|---|---|
1 | 2 | 3 | 4 | 5 | 6 | ||
Procedure | 176 | × | × | × | × | × | × |
Hospital Group | 2 | × | × | × | × | × | |
Male | 2 | × | × | × | × | ||
ER-admit | 2 | × | × | × | × | ||
Transfer | 2 | × | × | × | × | ||
Paraplegia | 2 | × | × | × | |||
Stroke | 2 | × | × | × | |||
PPF | 2 | × | × | × | |||
CC | 2 | × | × | ||||
CHF | 2 | × | × | ||||
Dementia | 2 | × | × | ||||
Renal | 2 | × | × | ||||
Liver | 2 | × | |||||
Past A | 2 | × | |||||
Past MI | 2 | × | |||||
| |||||||
# Categories Lk | 176 = 176 | 176 × 2 = 352 | 176 × 24 = 2, 816 | 176 × 27= 22, 528 | 176 × 211= 360, 448 | 176 × 214 =2, 883, 584 | |
| |||||||
Imbalance | 0 | 12 | 52 | 176 | 664 | 1242 | |
% of maximum | 0.0% | 0.1% | 0.4% | 1.4% | 5.3% | 9.9% | |
Independence χ2 | 0.0 | 4.9 | 43.3 | 142.3 | 588.9 | 1158.7 | |
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Balance in 10,000 simulated randomized experiments with the same margins | |||||||
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Simulated χ2 statistics for independence | |||||||
| |||||||
Mean χ2 | 174.9 | 302.9 | 767.5 | 1062.0 | 1946.0 | 2814.0 | |
Minimum χ2 | 117.0 | 226.5 | 645.7 | 933.6 | 1777.0 | 2645.0 | |
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Simulated Total Imbalance | |||||||
| |||||||
Mean | 768 | 1051 | 1749 | 2086 | 3010 | 3812 | |
Minimum | 540 | 814 | 1500 | 1826 | 2752 | 3578 |