Years ago a friend introduced me to the idea that people were in general very bad at judging relative risk. He had watched a documentary about this and the subjective response people have to relative dangers was shown, for the most part, to be unrelated to the actual risk.
An easy example of this is the common fear of flying. Fear of getting a drive to the airport is unheard of even though the car ride is vastly more likely to result in injury or death than the flight. But the statistic is powerless against the misapprehension.
This will appear to be a departure from topic, but I had my periodic colonoscopy today. The doctor before arranging the procedure was very diligent in advising me of the relative risk. About 1 in 1000 such procedures lead to complications. Compared to the risk of undiagnosed colon cancer this seemed like no thing to me so I arranged for the procedure.
Afterward I was confused by the suggestion I got from a couple of other people that a 1 in 1000 risk of complications was significant. So, I considered their concerns and came up with this.
Given that I will live forever and I need a colonoscopy every 5 years; and given the certainty that in all those many many procedures 1 in every thousand, on average, will result in complications; I am certain to have a complication about every 5000 years. Moreover in all my future eternity that complication will on average occur about half way through each period at around the 2500-year mark. So, of all the undying multitudes of patients having routine scopes the average one shall expect a complication in about 2500 years, another in 7500 years and so on…
Of course one out of the next thousand colonoscopies is almost certainly going to have a complication. But in whole numbers this chance is 0%.
As an afterthought; on February 7, 2013, the day of the two giant snowstorms here, I had my specialist appointment with my gastroenterologist to get the procedure scheduled. On the way home, eastbound on Bayly St. at Kitney Dr. I hit a patch of black ice approaching the red light. I slid several metres before fetching up against the curb with a thump and skewing sideways. I nearly hit the car in the lane to my left and would have totaled the car had there been anyone in front of me. So while day surgery is unpleasant it is not risky. Driving on the other hand is one of the most dangerous things anyone ever does over and over again.