A formula to accompany the Birthday Problem

Let's look at the probabilities a step at a time.

Running this through a computer gives the chart below. Notice that a probability of over .5 is obtained after 23 dates!

chart of birthday probabilities
Notice that the probability is above .9
before the sample size reaches even 45.

Also, take a look at Lionel Mordecai's MathCAD programs. The algorithms are in an RTF file. It includes a nice graph of the output. He uses the programs in his statistics class.

Return to the Introduction.

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