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Voting Methods

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Many Ways to Pick a Winner – PowerPoint PPT presentation

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Title: Voting Methods


1
Voting Methods
  • Many Ways to Pick a Winner

2
The Way Things Are
  • We are all used to voting for whoever we want to
    win, with the person receiving the most votes
    declared the winner. This system works pretty
    well when there are only two candidates, but when
    there are more it creates some problems.
  • What is one problem that might happen when more
    candidates run?

3
Preference Ballots
  • In order to get more information from voters, a
    better way to hold an election is to allow voters
    to rank order the candidates rather than just
    pick their favorite. This shows not only who you
    want to win, but also who you want to lose (and
    everyone in-between).

4
Continued
  • A Preference Ballot would look something like
    this

5
Preference Table
  • When all of the preference ballots are counted,
    the results are placed in a preference table. The
    numbers at the top represent the number of people
    who have a ballot that looks like the one below
    that number.
  • If the four candidates were Fred, Wlima, Barney,
    and Dino

6
Continued
  • A Preference Table would look something like
    this

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
Who should win this election?
7
Plurality Method
  • This is the method that many people are most
    comfortable with. In this method, the person with
    the most 1st place votes wins (so only look at
    the 1st row to determine the winner.

8
Plurality (example)
  • In this example, Fred has 210 votes, Wilma has
    18590275 votes, and Barney has 315 votes.
    Therefore, Barney wins the election.

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
9
Borda Count
  • In a Borda Count, the different places are
    assigned different point values. Last place gets
    1 point, and it increases by 1 point every time
    you go up one place (i.e. 2nd to last equals 2
    points, next best place equals 3 points, etc.)
    The person with the most total points will win
    the election.

10
This is an example of the Borda count in action
11
Borda Count (example)
  • Here are the totals in this example
  • Fred4210 3500 290 2520 pts
  • Wilma 4275 3210 2315 2360 pts
  • Barney 4315 2210 1275 1955 pts
  • Dino 390 2185 1525 1165 pts
  • Fred wins the election

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
12
Homework, homework, homework!
  • P. 735-736 2, 3, 5, 7, 8, 11, 12

13
Voting, Day 2 How to pick a winner
14
Plurality with Elimination
  • In this method, you find the candidate with the
    fewest number of 1st place votes and eliminate
    them from the race. All the votes in that column
    move up one place (the 2nd place votes now become
    the 1st place votes)
  • This process continues until someone has a
    majority (or there is a tie)

15
Plurality with Elimination (example)
  • In this example, Dino has the fewest 1st place
    votes, so he is removed from the race, and the
    votes in that column move up one place.

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
16
Plurality with Elimination (example)
  • Fred now has the fewest first place votes, and is
    the next to go.

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F F
3rd choice B B W B
4th choice
17
Plurality with Elimination (example)
  • Since Wilma now has 21018590 485 votes, she
    has a majority and is declared the winner of the
    election.

Number of Votes 210 185 315 90
1st choice W W B W
2nd choice B B W B
3rd choice
4th choice
18
Election-swaying.com. Slapupsidethehead.com
19
Pairwise Comparison
  • In this method, you compare candidates two at a
    time and see who would win in each column. The
    candidate who would be victorious with a majority
    of the voters would win that comparison.
  • Each comparison victory is worth 1pt. Each tie is
    worth ½ pt. Whoever has the most points wins the
    election.

20
Pairwise Comparison (example)
  • In this example, there will be 6 different
    comparisons. The number is determined by
    n(n-1)/2, where n is the number of candidates.

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
21
Pairwise Comparison (example)
  • Between Fred Wilma, Fred wins in 525 votes,
    while Wilma wins in 275 votes, so Fred beats
    Wilma (and gets 1 pt).

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
22
Pairwise Comparison (example)
  • Between Fred Barney, Fred wins in 485 votes,
    while Barney wins in 315 votes, so Fred beats
    Barney (and gets 1 pt).

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
23
Pairwise Comparison (example)
  • Between Fred Dino, Fred wins in 525 votes,
    while Dino wins in 275 votes, so Fred beats Dino
    (and gets 1 pt).

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
24
Pairwise Comparison (example)
  • Between Wilma Barney, Wilma wins in 485 votes,
    while Barney wins in 315 votes, so Wilma beats
    Barney (and gets 1 pt).

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
25
Pairwise Comparison (example)
  • Between Wilma Dino, Wilma crushes Dino with 800
    votes to Dinos none, so Wilma defeats Dino
    soundly (and gets 1 pt).

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
26
Pairwise Comparison (example)
  • Between Barney Dino, Barney gets 525 votes to
    Dinos 275, so Barney defeats Dino (and gets 1
    pt).

Number of Votes 210 185 315 90
1st choice F W B W
2nd choice W F F D
3rd choice B D W F
4th choice D B D B
27
Pairwise Comparison (example)
  • The final totals in this election are
  • Fred 3 pts
  • Wilma 2 pts
  • Barney 1 pt
  • Dino 0 points
  • So Fred wins the election.

28
Hipster-election-2004.gif. Toothpastefordinner.com
29
Youve got Homework, Yes you do, Youve got
Homework Woo Hoo!
  • P. 735-737 12-14, 19-22, 24-30
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