Bacterial contamination of surgical patients can occur from bacteria that contaminate the scrub suits worn by surgical personnel. During surgery, these scrub suits are covered by surgical gowns. However, because this effort is not perfect, one presumably could gain an advantage if the contamination of scrub suits was reduced. One of the sources of the contamination of scrub suits is bacteria picked up when personnel leave the operating room, for example, to go to lunch.

Traditional practice is to wear a covergown over the scrub suit so as to minimize contamination while outside the operating room. However, no data supported the use of covergowns, which are expensive.

Therefore, Copp and coworkers* sought to obtain evidence on the effectiveness of covergowns and also to test related hypotheses about various strategies to reduce scrub suit contamination in the operating room. One of their hypotheses was that a fresh scrub suit put on after lunch break was more effective in reducing contamination than changing to street clothes for lunch and protecting the scrub suit in a clean wrap in a locker until it was put on for the afternoon shift. These two strategies were followed by two groups of 19 operating room personnel whose scrub suits were swabbed on the shoulder for bacterial cultures at four times during the day: start of shift, immediately before lunch, on return from lunch, and at the end of the shift (the data are in Table D-28, Appendix D). Is there evidence to support their hypothesis? Include a graph of the data.