QuestionFind the winner using plurality-with-elimination for candidates A, B, C. How does a vote change affect the outcome? Is monotonicity met?
Studdy Solution
STEP 1
Assumptions1. The number of votes for each preference order is given in the table.
. The plurality-with-elimination method is used for voting.
3. In the plurality-with-elimination method, the candidate with the least number of first-choice votes is eliminated in each round, and their votes are redistributed according to the next choice on each voter's ballot. This process continues until a candidate has a majority of the votes.
STEP 2
First, we need to count the number of first-choice votes for each candidate in the straw vote. The number of first-choice votes for each candidate is given in the first row of the table.
STEP 3
In the plurality-with-elimination method, the candidate with the least number of first-choice votes is eliminated in the first round. In this case, candidate C has the least number of first-choice votes and is therefore eliminated.
STEP 4
The votes for candidate C are redistributed according to the second choice on each voter's ballot. From the table, we can see that the second choice for the63 voters who voted for candidate C first is candidate A. Therefore, these63 votes are added to candidate A's total.
STEP 5
Now we compare the number of votes for candidates A and B. Candidate A has135 votes and candidate B has90 votes. Since candidate A has more votes, candidate A wins the straw vote.
For part b, we need to consider the change in votes mentioned in the problem.
STEP 6
In the actual election, the36 voters who originally voted , change their votes to . This means that candidate B gains36 first-choice votes, candidate A gains36 third-choice votes (which do not count in the plurality-with-elimination method), and candidate C loses36 first-choice votes.
STEP 7
We need to update the number of first-choice votes for each candidate to reflect this change.
STEP 8
Again, we eliminate the candidate with the least number of first-choice votes. In this case, candidate C has the least number of first-choice votes and is therefore eliminated.
STEP 9
The votes for candidate C are redistributed according to the second choice on each voter's ballot. From the table, we can see that the second choice for the27 voters who voted for candidate C first is candidate B. Therefore, these27 votes are added to candidate B's total.
STEP 10
Now we compare the number of votes for candidates A and B. Candidate A has72 votes and candidate B has153 votes. Since candidate B has more votes, candidate B wins the actual election.
For part c, we need to determine whether the monotonicity criterion is satisfied.
STEP 11
The monotonicity criterion states that if a voter changes their vote to increase the ranking of a candidate, it should not harm that candidate's chances of winning. In this case, when the36 voters changed their votes from to , candidate B's ranking increased. However, this did not harm candidate B's chances of winning; in fact, it helped candidate B win the election. Therefore, the monotonicity criterion is satisfied.
The winners of the straw vote and the actual election are candidate A and candidate B, respectively, and the monotonicity criterion is satisfied.
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