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Statistics can be intimidating, and seem difficult to understand. I like to go over them carefully, if I am going to use them to help a patient understand risks and benefits. In the Understanding and Communicating Risk article ninth March 2018 CFP, the statistics in Table 2 on the benefits of CT screening and lung cancer were particularly baffling. May I suggest some corrections?
AR in the control group = 16/1000 = 1.6%, not 1.66. similarly AR in the screened group = 13/1000 = 1.3%, not 1.33%. The ARR the becomes 1.6% - 1.3% = 0.3%, not 0.33%. The RRR is (1.6 - 1.3)/1.6 = 0.1875 or 18.75%, not 20%. Lastly, and most tellingly, the NNS is 1/0.3 or 333, an even bigger number needed to screen than the erroneous 308 reported.Competing Interests: None declared.