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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
(A) Histogram distribution of propensity scores before and after PSM between the study groups. (B) Covariate balance before adjustment and after PSM and IPW (inverse probability of treatment weighting). IPW, inverse-probability weighting; PSM, propensity-score-matching.