My last blog said “you should stay at home damn it.” Problem is, unless you are a millionaire survivalist, we all have to go out occasionally to the supermarket. So the question is, how can you reduce the odds of catching Covid 19? How can you feel reasonably safe psychologically and in reality? The answer is: you need to keep (and apply) a simple, but fundamental principle of probability, in mind.<\/p>\n\n\n\n

A fundamental probability principle says that when you want to find out the odds of two independent events happening, you multiply the probabilities of each one happening. Throw 1 die and ask for a 6, well the odds are 1\/6. Throw one die after another and ask for sixes on both – well that is (1\/6)*(1\/6) or 1\/36. Three dies it’s 1\/(6*6*6) or 1\/216 etc etc. When multiple independent events are involved, the probability of all of them happening goes down really fast. (But they can happen: I’m convinced Trump’s election required numerous independent events to have happened.) Anyway why is this relevant to our current horrid situation in general and shopping in particular?<\/p>\n\n\n\n

The point is that each action you (and your fellow shoppers) can think of to lower your risk is almost certainly an independent<\/b> event. Maintain 6 feet of distance from each person, risk of getting the virus goes down to 1\/x. Wipe down your cart gets you 1\/y. Wipe your hands after you leave the store with a wipe and wash your hands after you unpack (being careful to keep your hands away from your face until you wash them) 1\/z. \n\n\n\nBut most importantly: hope other shoppers wear masks themselves, pray your neighbor is “forced” to wear a mask by sane governors. That’s gets you 1\/N for a pretty big N it seems. All these three taken together gets you to 1\/(x*y*z*N), which is going to be pretty small for any reasonable projected values of x,y and z. (Take each one of them as 1\/5 and having your neighbor wear a mask as 1\/20, then you are at 1\/2500 already.)<\/p>\n\n\n\n

The moral: think of multiple actions that you and your fellow citizens can take to lower the risk in the outside world that are independent<\/b> of each other for when you have to go out. Everyone wearing a mask is clearly #1 on that<\/i> list…..<\/p>\n","protected":false},"excerpt":{"rendered":"

My last blog said “you should stay at home damn it.” Problem is, unless you are a millionaire survivalist, we all have to go out occasionally to the supermarket. So the question is, how can you reduce the odds of catching Covid 19? How can you feel reasonably safe psychologically and in reality? The answer … Continue reading “Multiplication of probabilities – or what to do when you have to go shopping.”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[6],"tags":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/posts\/77"}],"collection":[{"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/comments?post=77"}],"version-history":[{"count":7,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/posts\/77\/revisions"}],"predecessor-version":[{"id":105,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/posts\/77\/revisions\/105"}],"wp:attachment":[{"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/media?parent=77"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/categories?post=77"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/garycornell.com\/wp-json\/wp\/v2\/tags?post=77"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}