Lean Six Sigma. Health. NoSQL. Hadoop. Hazy. Statistics Education. 5 Statistics Problems That Will Change The Way You See The World - Walter Hickey. Once the population of an office hits 366 people, it's a certainty that two people in your office have the same birthday, since there are only 365 possible days of birth. Still, assuming that each birth date (except February 29) is equally likely, it turns out that once your office has 57 people in it there is a 99% chance that two of them share a birthday. When there is 23 people, that probability is 50%. Here's why. Instead of calculating the probability that two people share a birthday, instead calculate the converse, probability that two people don't share a birthday. Since these are mutually exclusive scenarios, first probability plus the second probability has to equal 1.
Here's how we figure this out, then. Select two people in the office. 365/365 x 364/365 x 363/365 x 362/365 x ... x 343/365 = 0.4927. So, the probability that nobody in an office of 23 people share a birthday is 0.4927, or 49.3%. Source: Better Explained. Can you trust political trends? If you plot up the presidential results since Reagan came along, you get something interesting: a nice little regression. Using results from 1980-2008 (excluding 1992), you would have predicted that Obama would win in 2012 with about 53 percent of the vote, close to the actual result of about 51 percent, which is pretty surprising considering this method does not take into account any consideration of economics, who the Republican nominee was, or anything else of that nature. Here's the graph: We should interpret this graph as showing that it has been a little less likely for the Republican to win the presidency in each successive cycle as of late.
In 2016, it will be even less likely than it was this year. However, unlikely does not mean impossible, and it would still be consistent with the long-term trend if a Republican wins in 2016. But how much faith should we put in political trends like this? Until 1932. But that's not fair! And that's the point. A few more considerations below. Learning Analytics. Big Data. Pigeons Rival Primates In Number Task.