ACTIVITY - CHANGING PROBABILITIES WHEN NEW INFORMATION IS AVAILABLE
(from DeGroot, 1970)

The point of this activity is to demonstrate that probabilities that we assign are conditional on our current knowledge. As we learn and gain more information, our probabilities about statements can change. Later, we will introduce a formula, Bayes' rule, which will tell us how to compute new probabilities when we get information.

HOW LARGE IS PENNSYLVANIA?

  1. Consider the area, in square miles, of Pennsylvania. The table below lists four statements about the state's size.

    PERIOD PROBABILITY
    less than 5,000 square miles
    between 5,000 and 50,000 square miles
    between 50,000 and 100,000 square miles
    over 100,000 square miles


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Page Author: Jim Albert (© 1996)
albert@bayes.bgsu.edu
Document: http://www-math.bgsu.edu/~albert/m115/probability/penn1.html
Last Modified: November 24, 1996