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Table 1 A summary of selection bias prior to matching and bias reduction post matching

From: Propensity score interval matching: using bootstrap confidence intervals for accommodating estimation errors of propensity scores

Matching Method Sample Size SB for Logit of PS (%) PBR for Logit of PS (%) Average of Absolute SB across 74 Covariates (%) Average of PBR across 74 Covariates (%)
Prior to Matching nR = 1990 nU = 4327 78.73 16.22
Post Matching
Nearest Neighbor nR = nU = 1990 30.23 75.21 4.84 53.32
Optimal nR = nU = 1990 30.23 75.21 4.91 55.15
Mahalanobis Caliper nR = nU = 1701 61.04 51.79 10.16 25.70
Caliper nR = nU = 1539 1.96 98.41 1.00 76.78
50 % Interval nR = nU = 1483 −2.89 97.69 1.43 76.50
68 % Interval nR = nU = 1538 −0.46 99.64 1.25 79.24
95 % Interval nR = nU = 1713 9.52 92.55 1.33 79.12