We are gamblers, you and me.  With our very first breath, we begin assessing our surroundings and playing the odds for survival and pleasure.  We strive to amass data on what works to our benefit, and what doesn’t.  Unexpected outcomes (aka “outliers”) might be pleasant surprises or not-so-pleasant disappointments – either way, most of us seek the middle ground, regressing toward the mean (aka “reversion to mediocrity”).

Although we place our trust in what will work based on our assembled knowledge and experience, this is not always wise.  Often our well-honed intuition fails, leaving us dumbfounded.  One quintessential example is the familiar Birthday Paradox.

If 23 or more people are gathered together – like in a classroom or at a cocktail party – the odds are better than 50-50 that two will have the same birthday.  Given that there are 365 (not counting leap year) possible birthdays, how is this even possible?  At a very large party, with 366 people in attendance, then at least 2 would share a birthday – that much is clear – but only with some clever math can we prove the aforementioned counterintuitive odds.  See the link above for the math. <continue reading>