Although both groups had similar technical abilities preintervention [ DP : median score , 13.5 ( 9.3-15 .0 ) ; control : median score , 14.5 ( 9.3-17 .8 ) ; P = 0.45 ] , the DP residents had a superior technical performance postintervention [ DP : median score , 17.0 ( 15.3-18 .5 ) ; control : median score , 12.5 ( 7.5-14 .0 ) ; P = 0.03 ] .