@@@ A Simple Overview of Probability & Odds @@@

 

Definition:  Probability is concerned with events of chance or uncertainity.  ( Click on Probability! )

Probabilities are normally and usually represented as fractions e.g.            2/3     or      4/5

 

Scale of Probability:          Impossible                      Maybe                  Certain

                                             |-------------------------|-----------------------|

                                             0          Low             ½             High           1

 

Sample Space (Universe of Event)

 

         A listing or diagram of all possible outcomes from an experiment or occurrence.

 

Specific Event (Subset of Universe)

 

         Simple (single event)    or   Non-Simple (multiple events) of chance.

 

Types of Probabilities for an Experiment (Event) of Chance or Uncertainity. 

P = Probability     * = Not      P* = Not Probability

 

 

Probability Experiment: Tossing a Die

onto a table or the floor.

 

 

Since a Die is a Cube with 6 faces:

1,  2,  3,  4,  5,  6

   

 

@@@ Probability of Success = (Success / Total )         Probability of Failure* = ( Failure / Total )* @@@

 

 

 

P (2) = 1/6

 

 

P (Odd) = 3/6

 

 

P (N<5) = 4/6

 

 

P* (2) = 5/6

 

 

P* (Odd) = 3/6   

 

 

P* (N<5) = 2/6

 

 

P (R)  È  P*(R)  = 1              P (R)  Ç  P*(R)  = 0

 

 

 

The Sum of P and P* equals 1.              The intersection of P and P* equals 0.

 

 

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Definition:  Odds represents the probability of an event occurring and/or happening.  ( Click on Odds! )

 

Odds are normally and usually represented as ratios  e.g.       2:3     or      2 to 3

 

 

 

Summary of Odds: Die Experiment

Tossing a Die with 6 faces onto floor.

 

 

Since a Die is a Cube with 6 faces:

1,  2,  3,  4,  5,  6

 

 

 

Simple Example of the Odds for the above Experiment of Chance or Uncertainity.      

Odds represent a ratio of Probabilities.      Thus represent Odds then reduce as ratios.

 

 

Odds in favor of Two event:          Of (N=2) =  1/6 : 5/6    =  1 : 5  or   1 to 5

 

Odds against Two event:                      Oa (N=2) =  5/6 : 1/6    =  5 : 1  or   5 to 1

 

 

Odds in favor of Odd event:          Of (N is Odd) =  3/6 : 3/6      =  3 : 3  or   3 to 3

 

Odds against Odd event:                     Oa (N is Odd) =  3/6 : 3/6     =  3 : 3  or   3 to 3

 

 

Odds in favor of N<5 event:          Of (N<5) =  4/6 : 2/6    =  4 : 2  or   4 to 2

 

Odds against N<5 event:                      Oa (N<5) =  2/6 : 4/6    =  2 : 4  or   2 to 4

 

 

Thus using Probabilities to develop Odds readily shows that it is more likely to not get a Two.

 

      

Tom Love                    Malone College                Fall 2003

 

Reference for this information on P & O:  Fundamentals of Mathematics by Edwin I. Stein