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. 2021 May 24;21:109. doi: 10.1186/s12874-021-01282-1

Fig. 3.

Fig. 3

Candidate covariate standardized mean differences after large-scale propensity score matching (PSM) and cardinality matching (CM). Fine balance: exact marginal distributional balance. Violin plots illustrate kernel probability density; the width of the shaded area represents the proportion of observations with the corresponding y-axis value