Giving formulae as such without appropriate context is bound to confuse students.
-----Original Message----- From: Charles J. Masenas <email@example.com> To: Tad Watanabe <firstname.lastname@example.org> Cc: Math-Teach <email@example.com> 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. > >------- >Regards, >Charles J. Masenas > > >