In an experiment to compare two different surgical procedures for hernia repair (“A Single-Blinded, Randomized Comparison of Laparoscopic Versus Open Hernia Repair in Children,” Pediatrics [2009]: 332–

336), 89 children were assigned at random to one of the two surgical methods. The researchers relied on the random assignment of subjects to treatments to create comparable groups with respect to extraneous variables that they did not control. One such extraneous variable was age. After random assignment to treatments, the researchers looked at the age distribution of the children in each of the two experimental groups (laparoscopic repair

(LR) and open repair (OR)). The accompanying figure is from the paper.

LR 16 14 12 10 8

6 4

2 0

OR Age, y Based on this figure, has the random assignment of subjects to experimental groups been successful in creating groups that are similar with respect to the ages of the children in the groups? Explain.