1. 1.5 Weighted Voting and Voting Power
Ms. Magné́
Discrete Math

2. Review of Group Ranking
Plurality Majority Borda Runoff Sequential Runoff Condorcet Pairwise Approval

3. Weighted Voting
Weighted Voting – this occurs when some members of the voting population have more votes then others.

4. Weighted Voting
Ex. The student council is composed of one representative from each class. Each member gets votes proportionate to their class size. The sophomore representative gets 5 votes, the junior gets 3, and the senior gets 3. Six votes are needed to pass an issue.
1) List all the coalitions (all possible collections
of votes)
2) List all winning coalitions

5. Essential Members
Essential Members – members who are necessary for an issue to pass. (If a member is taken out of a coalition and there are no longer enough votes to pass, then the member is said to be essential)
3) Who are the essential members in the
coalition {So, Sr; 8}?
4) Who are the essential members in the
coalition {So, Jr, Sr; 11}?

6. Power Index
Power Index – a measure of a members power. A member’s power index is equal to the number of coalitions a member is essential to.
5) List the power index for each member
of the student council.
So. =
Jr. =
Sr. =