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9. Graphical method example ( Enter your problem )
  1. Method & Example-1
  2. Example-2

1. Method & Example-1





Method
graphical method Steps (Rule)
Step-1: This method can only be used in games with no saddle point, and having a pay-off matrix of type n`xx`2 or 2`xx`n.
Step-2: The example is used to explain the procedure.

Example-1
1. Find Solution of game theory problem using graphical method
Player A\Player BB1B2
A11-3
A235
A3-16
A441
A522
A6-50


Solution:
1. Saddle point testing
Players
Player `B`
`B_1``B_2`
Player `A``A_1` 1  -3 
`A_2` 3  5 
`A_3` -1  6 
`A_4` 4  1 
`A_5` 2  2 
`A_6` -5  0 


We apply the maximin (minimax) principle to analyze the game.

Player `B`
`B_1``B_2`Row
Minimum
Player `A``A_1` 1  -3 `-3`
`A_2` [3]  5 `[3]`
`A_3` -1  6 `-1`
`A_4` (4)  1 `1`
`A_5` 2  2 `2`
`A_6` -5  0 `-5`
Column
Maximum
`(4)``6`


Select minimum from the maximum of columns
Column MiniMax = (4)

Select maximum from the minimum of rows
Row MaxiMin = [3]

Here, Column MiniMax `!=` Row MaxiMin

`:.` This game has no saddle point.



Solution using graphical method
First, we draw two parallel lines 1 unit distance apart and mark a scale on each.
The two parallel lines represent strategies of player `B`.

If player `A` selects strategy `A_1`, player `B` can win 1 or -3 units depending on B's selection of strategies.

The value 1 is plotted along the vertical axis under strategy `B_1` and the value -3 is plotted along the vertical axis under strategy `B_2`.

A straight line joining the two points is then drawn.
Similarly, we can plot strategies `A_2,A_3,A_4,A_5,A_6` also. The problem is graphed in the following figure.





The lowest point `V` in the shaded region indicates the value of game. From the above figure, the value of the game is `3.4` units.

1. The point of optimal solution occurs at the intersection of two lines
`E_2 = 3p_1 +5p_2`

`E_4 = 4p_1 +p_2`

Comparing the above two equations, we have
`3p_1 +5p_2 = 4p_1 +p_2`

Substituting `p_2 = 1 - p_1`

`3p_1 +5(1 - p_1) = 4p_1 +(1 - p_1)`

Solving `p_1=4/5`

`p_2=1-p_1=1-4/5=1/5`

Substituting the values of `p_1` and `p_2` in equation `E_2`

`V = 3(4/5) +5(1/5)=17/5`


2. The point of optimal solution occurs at the intersection of two lines
`L_2 = 3q_1 +4q_2`

`L_4 = 5q_1 +q_2`

Comparing the above two equations, we have
`3q_1 +4q_2 = 5q_1 +q_2`

Substituting `q_2 = 1 - q_1`

`3q_1 +4(1 - q_1) = 5q_1 +(1 - q_1)`

Solving `q_1=3/5`

`q_2=1-q_1=1-3/5=2/5`

Substituting the values of `q_1` and `q_2` in equation `L_2`

`V = 3(3/5) +4(2/5)=17/5`




This material is intended as a summary. Use your textbook for detail explanation.
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