Tuesday, January 29, 2008

Binomial or Poisson?

I found the following handy tip on Jonathan Deane's site (University of Surrey):

  • If a mean or average probability of an event happening per unit time/per page/per mile cycled etc., is given, and you are asked to calculate a probability of n events happening in a given time/number of pages/number of miles cycled, then the Poisson Distribution is used.
  • If, on the other hand, an exact probability of an event happening is given, or implied, in the question, and you are asked to caclulate the probability of this event happening k times out of n, then the Binomial Distribution must be used.
He also has some sample problems on that page what are worth a try for midterm practice.

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