Lawyers continuously deal with concepts of probability. Understanding probabilities can be an extremely useful way to persuade, craft useful analogies, and – in some cases – either create or disprove reasonable doubt.

**Probability concepts can be particularly powerful when they yield couterintutive results.** One such example is the “birthday paradox.”

**Quick – how many people must there be in a random group before we can expect that at least one pair shares the same birthday? **

One might quickly (and correctly, albeit inefficiently) reason the number has to be 367 or less. But most would be surprised that a 99% probability is reached with just 57 people, and a 50% probability with just 23.

Note: This is NOT the same question as: What are the odds that someone in a group will have the same birthday as mine? The birthday paradox deals with *any* person in a group matching *any* one of the others, not matching one in particular. The chances of the latter are far less likely.

For those of you (uber-cool-in-a-math-nerd-sort-of-way) folks who are interested in the actual calculations, you can tip your hat to your old STAT101 professor here.

For those not as interested in the details, here are a few neat examples using the Academy Award winners as a proxy for a random group of people. Ask yourself if you’d have accurately guessed the number of birthday pairs:

* Of all the actors to win the Academy Award for Best Actor, 6 pairs share the same birthday.

* Of all the actresses to win the Academy Award for Best Actress, 3 pairs share the same birthday.

* Of all the directors to win the Academy Award for Best Director, 5 pairs share the same birthday.