Saturday, February 14, 2009

Probability: Events, Outcomes, and Sample Spaces

Probability is one of the least intuitive aspects of statistics. If it wasn't, Casinos wouldn't net the billions of dollars they do each year.

What do we need to know to get a grounding in probability?

The first thing is the sample space, this is the set of all possible outcomes. For a coin it is heads or tails, for a die it is [1,2,3,4,5,6] and for the height of a person it is [x:x>0]

Outcomes are the result of any random event that we want to predict, i.e. we roll a die and a 2 comes up.

An Event is a desired outcome and is often denoted with a capital letter. For the dice we can define the event, A, as A=2.

Imagine we roll the die again and a 5 is the outcome. Then our desired event did not happen.

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