Fig. 3

Graphical presentation of relationships between types of the scheduled surgery and patient’s anticipated pain. The invasiveness of surgical procedures graded by a clinical prediction model established by Janssen and his colleageus [22], as types of operation were grouped into the lowest, low, moderate, high and highest expected pain surgery. The median value of anticipated numeric rating scale (NRS) in the lowest expected pain surgery group was significantly increased in comparison to the other groups (*P < 0.05 and **P < 0.001; as analyzed using the Kruskal-Wallis test, followed by the Dunn’s post-hoc test). Results are presented as box-and-whisker plots, in which the horizontal solid lines of boxes indicate the 75th percentile, median and 25th percentile of the distribution, and the upper and lower whiskers indicate the maximal and minimal values. Dotted lines indicate the mean values