1. Day 3: Plurality with elimination, Runoff method, Condorcet criterion (Txt:1.2,1.3 & SOL: DM.8)
Classwork:
p.33 (27abc run off, 29ab run off, 31,
33ab run off)
Homework (day 3):
p.33 (28 run off, 30 run off, 32, 34ab run off)
Project Presentations next block

2. Plurality with Elimination (Sequential Run-Off)
Each voter votes for one candidate.
A candidate that receiving the majority of the votes is declared the winner.
If no candidate receives a majority of the votes, then the candidate/candidates with the fewest votes is dropped from the ballot and a new election is held.
You follow this process until a candidate receives the majority of votes.

3. Ex How many voters are there? 336 7 5 3 9
1st C A B D
2nd
3rd
4th
How many voters are there? 33
Therefore how many are needed for a majority? 17
A = 10, B = 9, C = 11, D = 3
Who has the majority?
No one so D looses and is eliminated

4. Therefore A wins!!!! 6 7 5 3 9 1st C A B D 2nd 3rd 4th 6 10 5 3 9 1 C6 10 5 3 9 1 C A B 2
Eliminate D 22 11 1 A C 2 6 10 5 3 9 1 C A 2
Eliminate B
Therefore A wins!!!!

5. Run – off Method https://www.youtube.com/watch?v=RsT1NYsPn2o
You only keep the top two first place voters and have an election between those two.

6. Ex How many voters are there? 28 How many votes does each person have?
A = 6, B = 5, C = 8, D = 0 E = 9
Therefore how many are needed for a majority? 15
Who should you keep?
C and E 8 9 5 4 2
1st C E B A
2nd D
3rd
4th
5th 8 9 5 4 2 1 C E 19 9 1 C E 2
4) Who is the winner? C

7. Condorcet Criterion
1. If candidate X can defeat each of the other candidates in a head-to-head vote, then X is the winner of the election. Say you have candidates: A,B,C,D First say A vs. B if B wins Then try B vs. C if B wins Then try B vs. D However, if C won in step 2 then you have to go back and check C vs. A and C vs. D

8. Ex A B C
A versus B
3 to B wins A B C
B versus C
5 to 2 B wins A B C

9. This video demonstrates determining a winner in an election by plurality, borda count, instant run-off, and sequential pairwise voting. With each method, the winner is different, even though the votes have remained the same.
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