Incorrect NNT calculation. The Medicine by the Numbers “Tap Water vs. Sterile Saline for Wound Irrigation” (August 1, 2015, online only) incorrectly calculated a number needed to treat statistic for decreasing wound infection with tap water. This error stemmed from the Medicine by the Numbers being inadvertently based on an uncorrected version of the Cochrane review. The box at the top should not have included the line “Number needed to treat = 36 to prevent wound infection,” and under Harms it should have read “None were harmed by using tap water.” In the second paragraph of the Narrative section, the sentences related to this should have read: “In adults (1,328 participants), there was a nonsignificant decrease in wound infection in the tap water group (relative risk = 0.66; 95% confidence interval [CI], 0.42 to 1.04). In children (535 participants), there was a nonsignificant increase in wound infections in the tap water group (relative risk = 1.07; 95% CI, 0.43 to 2.64).” The online version of this department has been corrected.