Find Solution of game theory problem using arithmetic method
Player A\Player B | B1 | B2 | B3 |
A1 | 1 | 7 | 2 |
A2 | 6 | 2 | 7 |
A3 | 5 | 1 | 6 |
Solution:
1. Saddle point testing
Players
| | | Player `B` | | |
| | | `B_1` | `B_2` | `B_3` | | |
Player `A` | `A_1` | | 1 | 7 | 2 | |
`A_2` | | 6 | 2 | 7 | |
`A_3` | | 5 | 1 | 6 | |
We apply the maximin (minimax) principle to analyze the game.
| | | Player `B` | | |
| | | `B_1` | `B_2` | `B_3` | | Row Minimum |
Player `A` | `A_1` | | 1 | 7 | 2 | | `1` |
`A_2` | | (6) | [2] | 7 | | `[2]` |
`A_3` | | 5 | 1 | 6 | | `1` |
| Column Maximum | | `(6)` | `7` | `7` | | |
Select minimum from the maximum of columns
Column MiniMax = (6)
Select maximum from the minimum of rows
Row MaxiMin = [2]
Here, Column MiniMax `!=` Row MaxiMin
`:.` This game has no saddle point.
2. Dominance rule to reduce the size of the payoff matrix
Using dominance property
| | | Player `B` | | |
| | | `B_1` | `B_2` | `B_3` | | |
Player `A` | `A_1` | | 1 | 7 | 2 | |
`A_2` | | 6 | 2 | 7 | |
`A_3` | | 5 | 1 | 6 | |
row-3 `<=` row-2, so remove row-3
| | | Player `B` | | |
| | | `B_1` | `B_2` | `B_3` | | |
Player `A` | `A_1` | | 1 | 7 | 2 | |
`A_2` | | 6 | 2 | 7 | |
column-3 `>=` column-1, so remove column-3
| | | Player `B` | | |
| | | `B_1` | `B_2` | | |
Player `A` | `A_1` | | 1 | 7 | |
`A_2` | | 6 | 2 | |
reduced matrix
| | | Player `B` | | |
| | | `B_1` | `B_2` | | |
Player `A` | `A_1` | | 1 | 7 | |
`A_2` | | 6 | 2 | |
Using arithemetic method to get optimal mixed strategies for both the firms.
| | | Player `B` | | |
| | | `B_1` | `B_2` | | |
Player `A` | `A_1` | | 1 | 7 | | `|6-2|=4` `:. p_1=(4)/(6+4)=2/5` |
`A_2` | | 6 | 2 | | `|1-7|=6` `:. p_2=(6)/(6+4)=3/5` |
| | | `|7-2|=5` `:. q_1=(5)/(5+5)=1/2` | `|1-6|=5` `:. q_2=(5)/(5+5)=1/2` | | |
1. Find absolute difference between the two values in the first row and put it against second row of the matrix
`|1-7|=6`
2. Find absolute difference between the two values in the second row and put it against first row of the matrix
`|6-2|=4`
`:. p_1=(4)/(6+4)=2/5`
`:. p_2=(6)/(6+4)=3/5`
3. Find absolute difference between the two values in the first column and put it against second column of the matrix
`|1-6|=5`
4. Find absolute difference between the two values in the second column and put it against first column of the matrix
`|7-2|=5`
`:. q_1=(5)/(5+5)=1/2`
`:. q_2=(5)/(5+5)=1/2`
Hence, firm `A` should adopt strategy `A_1` and `A_2` with 40% of time and 60% of time respectively.
Similarly, firm `B` should adopt strategy `B_1` and `B_2` with 50% of time and 50% of time respectively.
Expected gain of Firm A
`(1)` `1 xx 2/5+6 xx 3/5 = 4 ,` Firm `B` adopt `B_1`
`(2)` `7 xx 2/5+2 xx 3/5 = 4 ,` Firm `B` adopt `B_2`
Expected loss of Firm B
`(1)` `1 xx 1/2+7 xx 1/2 = 4 ,` Firm `A` adopt `A_1`
`(2)` `6 xx 1/2+2 xx 1/2 = 4 ,` Firm `A` adopt `A_2`
This material is intended as a summary. Use your textbook for detail explanation.
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