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July 29th, 2016, 11:00 AM  #1 
Senior Member Joined: Oct 2013 From: New York, USA Posts: 620 Thanks: 85  Math Mistakes You've Seen In Everyday Life
What math mistakes have you seen people make in everyday life? I'm talking about concepts that do not require a high level of education and can be useful even if your career has nothing to do with math. Here's an example. A person thought the probability of a draw in a soccer game would be 1/3 because there are three possible outcomes. When introducing probability to students, examples of coins and dice are given that involve equally likely outcomes, but people should know that not all outcomes are equally likely. To give an example of two outcomes that are luckily not anywhere near equally likely, when you get in your car, you could get to your destination, or you could die in a car accident. I also saw somebody doing college admissions make an arithmetic mistake that helped a student get accepted. A student needed at least 15 points out of 20 from four categories worth up to 5 points each. The person evaluating the student mistakenly wrote that 3 + 3 + 4 + 4 = 16. I don't remember what order the 3s and 4s were in, but order is irrelevant in addition.

July 29th, 2016, 02:09 PM  #2 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 13,480 Thanks: 950  
July 29th, 2016, 04:24 PM  #3 
Math Team Joined: Nov 2014 From: Australia Posts: 689 Thanks: 244 
I don't think this counts as real life, but it's a good story anyway. When I was in college (years 11 and 12), my friends and I went to the maths staffroom to ask our teacher a question about our assignment. While we were waiting for her to be available, a different teacher turned to us and asked "What's 3x3?" We all looked at each other and said "9". He held up the test he was marking and said "According to this person, it's actually 6." 
July 29th, 2016, 07:52 PM  #4 
Banned Camp Joined: Jun 2014 From: Earth Posts: 945 Thanks: 191 
Years ago I witnessed a TV commercial for a local circus with a boy announcing dates something such as the 11th through the 14th of that month. At the end of the commercial, he held up three fingers and shouted, "That's three days!" A day or two later, after the commercial was reshot, the same boy appeared in a TV commercial and at the end of the commercial, he held up four fingers and shouted, "That's four days!" 
July 30th, 2016, 11:33 AM  #5 
Senior Member Joined: Oct 2013 From: New York, USA Posts: 620 Thanks: 85 
Football announcers take a team's takeaways  giveaways and incorrectly call it "turnover ratio." It's "turnover differential." Several sports say "winning percentage," but it's expressed as a decimal out of 1,000, not out of 100.

July 30th, 2016, 11:48 AM  #6 
Senior Member Joined: Dec 2012 From: Hong Kong Posts: 853 Thanks: 311 Math Focus: Stochastic processes, statistical inference, data mining, computational linguistics 
People confusing odds and probability, and interpreting pvalues as the posterior probabilities of the null hypothesis being true.


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