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Topic: Re: and/or
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Chi-Tien Hsu

Posts: 144
Registered: 12/6/04
Re: and/or
Posted: Nov 24, 1997 4:16 AM
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Giving formulae as such without appropriate context is bound
to confuse students.


-----Original Message-----
From: Charles J. Masenas <>
To: Tad Watanabe <>
Cc: Math-Teach <>
Date: Friday, November 21, 1997 11:23 AM
Subject: Re: and/or

>Message Dated: Thu, 20 Nov 1997 19:05:38 EST
>>> This has very little to do with Josh's original post, but many of my
>>> students find it extremely confusing the two formulas (formulae?):
>>> P(A or B) = P(A) + P(B) - P(A and B)
>>> P(A and B) = P(A)*P(B|A)

>It might help to use Venn diagrams for sample spaces. For example, the
>events associated with drawing aces in a deck of cards can be viewed
>as an area in sample space. The probability of drawing an ace or a
>diamond can be translated to an area in sample space. Each of the
>terms in the above formulas translates to an area.
>Charles J. Masenas

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