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500   CHAPTER 12 SIMULATION



                                      Table 12.6 Random Generation of Ten Values for First-Year Demand
                                      Trial                     Random Number                 Demand
                                       1                            0.7005                     17,366
                                       2                            0.3204                     12,900
                                       3                            0.8968                     20,686
                                       4                            0.1804                     10,888
                                       5                            0.4346                     14,259
                                       6                            0.9605                     22,904
                                       7                            0.5646                     15,732
                                       8                            0.7334                     17,804
                                       9                            0.0216                      5,902
                                      10                            0.3218                     12,918




                                     values for demand. Note that random numbers less than 0.5 generate first-year
                                     demand values below the mean and that random numbers greater than 0.5 generate
                                     first-year demand values greater than the mean.

                                     Running the Simulation Model Running the simulation model means implementing
                                     the sequence of logical and mathematical operations described in the flowchart in
                                     Figure 12.3. The model parameters are E249 per unit for the selling price, E400 000
                                     for the administrative cost and E600 000 for the advertising cost. Each trial in the
                                     simulation involves randomly generating values for direct labour cost, parts cost and
                                     first-year demand and for calculating profit. The simulation is complete when a
                                     satisfactory number of trials have been conducted.
                                       Using the simulated results in Tables 12.4, 12.5 and 12.6, the results for the first
                                     trial will be:

                                                            Direct labour cost : c 1 ¼ 45
                                                            Parts cost :   c 2 ¼ 86:25
                                                            First-year demand : x ¼ 17; 366

                                     And with the profit equation:


                                                          Profit ¼ð249   c 1   c 2 Þx   1 000 000


                                     we obtain:
                                                  Profit ¼ð249   45   86:25Þ17 366   1 000 000 ¼ 1 044 847
                                       Table 12.7 shows the simulated profit over the first ten trials. We see that profit
                                     could be as high as E1 822 231, although we also note that in one trial we made a loss
                                     of E319 972. We note also that the average values for labour cost, parts cost and
                                     first-year demand are fairly close to their means of E45, E90 and 15 000, respec-
                                     tively. Clearly with only ten trials, we cannot expect to replicate the decision problem
                                     accurately. A much larger number of trials is needed to allow the results to better
                                     approximate to the probability distributions we have used. To do this we need to use
                                     computer-based simulation.







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