Wednesday, November 4, 2009

Dicey puzzle

Your friend rolls either one, two, or three dice (n=1, n=2 or n=3). Each die is a normal cube with six sides, displaying a number between 1 and 6. She doesn't tell you what n is, but tells you that the sum of the numbers on the dice is 7.

For example, she could have rolled 4 and 3 with n=2; or perhaps 5, 1, and 1 with n=3 etc. Obviously, n cannot be equal to one.

What are the odds of n=2 v/s n=3 given that the sum is 7?

Answer coming up in a week, but this is an example of simple Bayesian analysis.

Credits: picture from

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