The case of the matching keys
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understandinguncertainty.org was produced by the Winton programme for the public understanding of risk based in the Statistical Laboratory in the University of Cambridge. The aim was to help improve the way that uncertainty and risk are discussed in society, and show how probability and statistics can be both useful and entertaining.
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When I was at university my student flat had the same door key as my parent's house. The two places were thirty miles apart and completely independent of one another but both happened to be my place of residence at the same time. They were both Yale locks and the keys were completely interchangeable.
I've always wondered how many combinations of Yale key there are and how much tolerance there is to keys working in locks that they aren't quite correct for. I believe this concept is known as key relevance but my maths isn't up to the job of calculating an actual probability.
This web page seems to suggest that for a six pin lock the odds of two people having the same key are 300,000,000 to one but doesn't actually show the calculations:
https://www.locksonline.co.uk/community/will-that-be-5-pin-of-6-pin-sir-ask-this-of-your-own-security.html
Date submitted:Mon, 09 Apr 2018 15:37:06 +0000Coincidence ID:9974
