At posttraining the CSC group ( n = 9 ) scored significantly higher on a procedure-specific skill scale compared with the CT group ( n = 9 ) [ median , 3.90 ( interquartile range , 3.68-4 .30 ) vs 3.60 ( 2.98-3 .70 ) , P = 0.017 ] , and made fewer technical errors [ 10 ( 7-13 ) vs 18 ( 13-21 ) , P = 0.003 ] .