14.1 Voting Methods
I. Elections with 2 alternatives
Suppose we poll the class to see whether you prefer the pizza at Domino’s or Pizza Hut.
How should
we determine the winner?
This is called
majority rule
.
E.g. If there are 49 voters, how many are needed to constitute a majority?
E.g. If there are 50 voters, how many are needed to constitute a majority?
II. Elections with more than 2 alternatives
Suppose we poll the class to see whether you prefer the pizza at Domino’s, Pizza Hut, Papa John’s,
Godfather’s or Little Caesars.
Suppose there are 55 students who vote as follows:
Domino’s
18
Little Caesars
9
Papa John’s
12
Godfather’s
6
Pizza Hut
10
The
plurality method
says to take the option with the most votes.
This would be Domino’s.
But often
elections require a majority of candidates to favor the winning option.
If this is the case, we could have a runoff
between the Domino’s and Papa John’s.
To do this, we would need to know how those who voted for Pizza
Hut, Godfather’s and Little Caesars rank the top two finishers.
Suppose we ask for even more information.
We ask each of the 55 voters to rank all 5 chains in order of preference.
After gathering all 55 rankings we see that many of the voters turned in the same ranking.
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 Fall '11
 PatriciaBishop
 pizza hut, Voting system, Plurality voting system, Pairwise comparison, Papa John

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