This unit covers quantitative analysis for decision making: decision environments, payoff and regret tables, decision making under uncertainty (maximax, maximin and minimax regret criteria) and decision making under risk (EMV, EPPI and EVPI), with worked stocking problems. Board exam questions, including graphical linear programming, are listed at the end by exam year, with marks in brackets.
Quantitative Analysis and Decision Making
The techniques used in analysing a problem which involve the use of numbers, symbols and mathematical expressions are called quantitative analysis or quantitative techniques.
Quantitative techniques are those statistical or programming techniques which provide the decision maker with a systematic and powerful means of analysis, based on quantitative data, in exploring policies for achieving pre-determined goals.
Decision making, also known as decision analysis, is the selection by the decision maker of the optimal strategy from the various options available to him.
Types of Decision-Making Environment
- Decision making under certainty
- Decision making under risk
- Decision making under uncertainty
Payoff and Regret
Payoff: the benefit obtained from a given combination of decision alternative (strategy) and state of nature.
Regret value: a quantitative measure of loss obtained by subtracting a particular payoff from the highest payoff, both belonging to the same state of nature.
Decision Making under Uncertainty
When probabilities of the states of nature are not known, one of the following criteria is applied to the payoff (or regret) table.
| Criterion | Attitude | Rule |
|---|---|---|
| Maximax | Optimistic | Find the maximum payoff of each strategy; select the strategy with the maximum of these maxima. |
| Maximin | Pessimistic | Find the minimum payoff of each strategy; select the strategy with the maximum of these minima. |
| Minimax regret | — | Build the regret table; find the maximum regret of each strategy; select the strategy with the minimum of these maxima. |
Payoffs in Stocking Problems
When a trader stocks \(S\) units and demand is \(D\) units, the payoff is:
where \(MP\) is the marginal profit and \(ML\) is the marginal loss per unit. For example, with CP = Rs. 10, SP = Rs. 15 and SV = Rs. 1: \(MP = 15 - 10 = \text{Rs. } 5\) and \(ML = 10 - 1 = \text{Rs. } 9\).
Decision Making under Risk
When the probabilities of the states of nature are known, the strategy with the maximum expected monetary value is selected.
- EMV — expected monetary value of a strategy.
- EPPI — expected profit with perfect information: the best payoff for each state of nature (the diagonal of a stocking payoff table), weighted by its probability.
- EVPI — expected value of perfect information: the maximum amount worth paying for perfect information.
Worked Examples
Example 1: Maximax, Maximin and Minimax Regret
| Strategy | \(N_1\) | \(N_2\) | \(N_3\) | Maximum | Minimum |
|---|---|---|---|---|---|
| \(S_1\) | 70 | 30 | 15 | 70 (max) | 15 |
| \(S_2\) | 50 | 45 | 10 | 50 | 10 |
| \(S_3\) | 30 | 40 | 20 | 40 | 20 (max) |
Regret table (column maxima 70, 45, 20):
| Strategy | \(N_1\) | \(N_2\) | \(N_3\) | Maximum regret |
|---|---|---|---|---|
| \(S_1\) | 0 | 15 | 5 | 15 (min) |
| \(S_2\) | 20 | 0 | 10 | 20 |
| \(S_3\) | 40 | 5 | 0 | 40 |
- Maximax: maximum of maxima is 70 → select \(S_1\).
- Maximin: maximum of minima is 20 → select \(S_3\).
- Minimax regret: minimum of maximum regrets is 15 → select \(S_1\).
Example 2: Stocking Decision (Demand 10–14 Units)
Payoff table (Rs.), with stock \(S\) and demand \(N\):
| Stock | \(N\) = 10 | 11 | 12 | 13 | 14 | Maximum | Minimum |
|---|---|---|---|---|---|---|---|
| \(S_1\) (10) | 400 | 400 | 400 | 400 | 400 | 400 | 400 (max) |
| \(S_2\) (11) | 380 | 440 | 440 | 440 | 440 | 440 | 380 |
| \(S_3\) (12) | 360 | 420 | 480 | 480 | 480 | 480 | 360 |
| \(S_4\) (13) | 340 | 400 | 460 | 520 | 520 | 520 | 340 |
| \(S_5\) (14) | 320 | 380 | 440 | 500 | 560 | 560 (max) | 320 |
Regret table (column maxima 400, 440, 480, 520, 560):
| Stock | 10 | 11 | 12 | 13 | 14 | Maximum regret |
|---|---|---|---|---|---|---|
| \(S_1\) | 0 | 40 | 80 | 120 | 160 | 160 |
| \(S_2\) | 20 | 0 | 40 | 80 | 120 | 120 |
| \(S_3\) | 40 | 20 | 0 | 40 | 80 | 80 |
| \(S_4\) | 60 | 40 | 20 | 0 | 40 | 60 (min) |
| \(S_5\) | 80 | 60 | 40 | 20 | 0 | 80 |
- Maximax: 560 → select \(S_5\) (stock 14).
- Maximin: 400 → select \(S_1\) (stock 10).
- Minimax regret: 60 → select \(S_4\) (stock 13).
Example 3: CP Rs. 24, SP Rs. 31, Demand 33–36
Salvage value is 0, so \(MP = 31 - 24 = \text{Rs. } 7\) and \(ML = 24 - 0 = \text{Rs. } 24\). For example, \(D = 33, S = 33\): \(33 \times 7 = 231\); \(D = 33, S = 34\): \(33 \times 7 - 1 \times 24 = 207\).
| Stock | \(N\) = 33 | 34 | 35 | 36 | Maximum regret |
|---|---|---|---|---|---|
| \(S_1\) (33) | 231 | 231 | 231 | 231 | 21 |
| \(S_2\) (34) | 207 | 238 | 238 | 238 | 24 |
| \(S_3\) (35) | 183 | 214 | 245 | 245 | 48 |
| \(S_4\) (36) | 159 | 190 | 221 | 252 | 72 |
Regrets are found from column maxima 231, 238, 245, 252 (for example, \(S_2\) at \(N = 33\): \(231 - 207 = 24\)). Maximax selects \(S_4\) (252), maximin selects \(S_1\) (231), and minimax regret selects \(S_1\) (21).
Example 4: SP Rs. 200, CP Rs. 140, Demand 12–17
\(MP = 200 - 140 = \text{Rs. } 60\), \(ML = 140 - 0 = \text{Rs. } 140\).
| Stock | 12 | 13 | 14 | 15 | 16 | 17 | Maximum | Minimum | Maximum regret |
|---|---|---|---|---|---|---|---|---|---|
| \(S_1\) (12) | 720 | 720 | 720 | 720 | 720 | 720 | 720 | 720 (max) | 300 |
| \(S_2\) (13) | 580 | 780 | 780 | 780 | 780 | 780 | 780 | 580 | 240 (min) |
| \(S_3\) (14) | 440 | 640 | 840 | 840 | 840 | 840 | 840 | 440 | 280 |
| \(S_4\) (15) | 300 | 500 | 700 | 900 | 900 | 900 | 900 | 300 | 420 |
| \(S_5\) (16) | 160 | 360 | 560 | 760 | 960 | 960 | 960 | 160 | 560 |
| \(S_6\) (17) | 20 | 220 | 420 | 620 | 820 | 1020 | 1020 (max) | 20 | 700 |
Maximax selects \(S_6\) (1020), maximin selects \(S_1\) (720), and minimax regret selects \(S_2\) (240).
Example 5: SP Rs. 25, CP Rs. 10, Demand 10–14
\(MP = 25 - 10 = 15\), \(ML = 10 - 0 = 10\).
| Stock | 10 | 11 | 12 | 13 | 14 | Minimum | Maximum regret |
|---|---|---|---|---|---|---|---|
| \(S_1\) (10) | 150 | 150 | 150 | 150 | 150 | 150 (max) | 60 |
| \(S_2\) (11) | 140 | 165 | 165 | 165 | 165 | 140 | 45 |
| \(S_3\) (12) | 130 | 155 | 180 | 180 | 180 | 130 | 30 (min) |
| \(S_4\) (13) | 120 | 145 | 170 | 195 | 195 | 120 | 30 (min) |
| \(S_5\) (14) | 110 | 135 | 160 | 185 | 210 | 110 | 40 |
Maximin selects \(S_1\) (150). Minimax regret gives a tie at 30, so either \(S_3\) or \(S_4\) may be selected.
Example 6: SP Rs. 500, CP Rs. 300, Demand 45–50
\(MP = 500 - 300 = \text{Rs. } 200\), \(ML = 300 - 0 = \text{Rs. } 300\).
| Stock | 45 | 46 | 47 | 48 | 49 | 50 | Maximum | Minimum | Maximum regret |
|---|---|---|---|---|---|---|---|---|---|
| \(S_1\) (45) | 9000 | 9000 | 9000 | 9000 | 9000 | 9000 | 9000 | 9000 (max) | 1000 |
| \(S_2\) (46) | 8700 | 9200 | 9200 | 9200 | 9200 | 9200 | 9200 | 8700 | 800 |
| \(S_3\) (47) | 8400 | 8900 | 9400 | 9400 | 9400 | 9400 | 9400 | 8400 | 600 (min) |
| \(S_4\) (48) | 8100 | 8600 | 9100 | 9600 | 9600 | 9600 | 9600 | 8100 | 900 |
| \(S_5\) (49) | 7800 | 8300 | 8800 | 9300 | 9800 | 9800 | 9800 | 7800 | 1200 |
| \(S_6\) (50) | 7500 | 8000 | 8500 | 9000 | 9500 | 10000 | 10000 (max) | 7500 | 1500 |
Optimistic approach (maximax) selects \(S_6\) (10,000); pessimistic approach (maximin) selects \(S_1\) (9,000); minimax regret selects \(S_3\) (600).
Example 7: EMV, EPPI and EVPI
CP = Rs. 30, SP = Rs. 50, salvage value 0, so \(MP = \text{Rs. } 20\) and \(ML = \text{Rs. } 30\). Demand 10–14 units has probabilities 0.10, 0.15, 0.20, 0.25 and 0.30.
| Stock | 10 (0.10) | 11 (0.15) | 12 (0.20) | 13 (0.25) | 14 (0.30) | EMV |
|---|---|---|---|---|---|---|
| \(S_1\) (10) | 200 | 200 | 200 | 200 | 200 | 200 |
| \(S_2\) (11) | 170 | 220 | 220 | 220 | 220 | 215 |
| \(S_3\) (12) | 140 | 190 | 240 | 240 | 240 | 222.5 (max) |
| \(S_4\) (13) | 110 | 160 | 210 | 260 | 260 | 220 |
| \(S_5\) (14) | 80 | 130 | 180 | 230 | 280 | 205 |
The maximum EMV (Rs. 222.5) corresponds to \(S_3\), so profit is maximised by stocking 12 units. The expected value of perfect information is Rs. 27.5.
Important Questions
2078 Exam
-
Solve the following linear programming problem graphically: [10 marks]
$$\begin{aligned} \text{Maximize } Z &= 30x + 50y \\ \text{subject to } x + y &\le 30 \\ x + 2y &\le 40 \\ x,\ y &\ge 0 \end{aligned}$$
2079 Exam
-
Solve the following linear programming problem: [10 marks]
$$\begin{aligned} \text{Minimize } Z &= 2x + 3y \\ \text{subject to } 5x + y &\ge 10 \\ 2x + 2y &\ge 12 \\ x + 4y &\ge 12 \\ x,\ y &\ge 0 \end{aligned}$$ -
(a) From the given payoff table, give the decision according to (i) maximax approach, (ii) maximin approach, (iii) minimax regret approach. [10 marks]
State of nature \(S_1\) \(S_2\) \(S_3\) \(N_1\) 400 200 700 \(N_2\) 100 600 300 \(N_3\) 500 300 100 (b) Two fair dice are rolled at the same time. What is the probability that the two faces turn up to show (i) a sum of 8 or 9, (ii) a sum less than 5?
2080 Exam
-
Solve the following problem graphically: [10 marks]
$$\begin{aligned} \text{Minimize cost } Z &= \text{Rs. } 20x + \text{Rs. } 30y \\ \text{subject to } 3x + 5y &\ge 45 \\ 2x + y &\ge 20 \\ x,\ y &\ge 0 \end{aligned}$$ -
The manager of a flower shop promises its customers delivery within four hours on all flower orders. All flowers are purchased on the previous day and delivered by 8.00 AM the next morning. The daily demand for roses is as follows: [15 marks]
Dozens of roses 70 80 90 100 Probability 0.1 0.2 0.4 0.3 The manager purchases roses for Rs. 10 per dozen and sells them for Rs. 30. All unsold roses are donated to a local hospital. Construct the payoff table. Also find EMV, EPPI and EVPI.
2082 Exam
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From the given payoff table, give the decision according to (i) maximax approach, (ii) maximin approach. [2 marks]
State of nature \(S_1\) \(S_2\) \(S_3\) \(N_1\) 50 30 90 \(N_2\) 70 80 40 \(N_3\) 20 40 20 -
Solve the following linear programming problem graphically: [10 marks]
$$\begin{aligned} \text{Minimize } Z &= 3x + 5y \\ \text{subject to } x + 2y &\ge 40 \\ x + y &\ge 30 \\ x,\ y &\ge 0 \end{aligned}$$ -
A vendor buys magazines at the rate of Rs. 10 and sells them at the rate of Rs. 15. Unsold magazines are worthless. The number of copies demanded and their corresponding probabilities are given below: [10 marks]
Copies demanded 200 210 220 230 240 Probability 0.19 0.16 0.25 0.27 0.13 (a) Determine the optimum stock level. (b) Calculate the maximum expected monetary value (EMV).
2083 Exam
-
Solve the following linear programming problem graphically: [10 marks]
$$\begin{aligned} \text{Maximize } Z &= 40A + 70B \\ \text{subject to } 3A + 3B &\le 36 \\ 5A + 2B &\le 50 \\ 2A + 6B &\le 60 \\ A,\ B &\ge 0 \end{aligned}$$