Fig. 2From: Propensity score analysis of lung cancer risk in a population with high prevalence of non-smoking related lung cancer a-b Histograms of propensity score distribution before and after propensity score matching. Distribution of the propensity scores before and after matching for group of family history of lung cancer (+) and group of family history of lung cancer (−). a presents histograms of unbalanced propensity score distribution in both groups before propensity matching. b presents histograms of balanced propensity score distribution in both groups after propensity matchingBack to article page