Research methods for managers

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Research methods for managers

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Abstract

The core problem in this case was related with a production planning again. How many S and how many P can I produce in order to maximize my profit with production's constraints like limited raw materials (USB ports), limited assembly hours and limited quality control hours. The main lesson of this case is graphical application and interpretation of linear programming method in order to search the optimal solution.

Make or buy:
In this case, things are more complicated because we had to determine how much to produce of each product and how much to buy of each same product (with a total units pre-defined) in order to minimize total cost (production' cost + purchase's cost). There were two types of constraints: productions' constraints and purchase's constraints. The mean shrewdness of this case is to name A, B, C, D, E production' units and A', B', C', D', E' purchasing' units in order to differentiate sources of units and constraints related in the same time.

Reallocating vehicles:
This case was a problem of re-distribution. The decision variable was how many bikes we need to move from X to Y (with a total of 8 different bike' stations). The objective was to minimize transportations cost. The number of bike had to correspond with a number of place pre-determined. It was constraints.

In this exercise, we have seen it exists two ways to solve the problem with two different answers. The manner to write the problem can influence your solution. It is essential to analyze your model after the resolution.

Introduction
During the seminar we worked with the following cases: Describe briefly the main lessons that you got from each one of these cases
Explain with several practical examples why sensitivity analyses (objective function coefficients and RHS constraints) are so important
Let's suppose that two constraints have the following shadow prices
In this slide 16 will find a network composed of nodes and arcs. White figures associated to each link represent the capacity of this link and red figures represent the cost of this link
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[...] Indeed, nurses can be or 3 but they can't be 1,32 or Finally, constraints are personnel cost. That is to say the weekly salary. f. Assigning planes Through this example, we have discovered combinations are not possible. In fact, before doing any model to compute and find the optimal solution, we have to take a critical look. Work too rapidly with a computer is not a good manner to process. In order to avoid strange solution, we have to eliminate by hand all the impossible combinations. [...]

[...] So thanks to this method, the result I found amounts to Slide 17 shows the same network in slide 16 but now the destination nodes have a given demand associated to these nodes (82 for node and 75 for node 8). Develop a LP model in order to answer the question at the bottom of the slide: which is the optimal distribution of flow (from source nodes via transshipment nodes to destination nodes) to satisfy demand in destination nodes and minimizing transportation costs? [...]

[...] Nevertheless, if we suppose we need 10 B for just 1 A to assemble our product, it is not obvious that doubling the constraint A's RHS is more interesting that doubling the constraint's B RHS. So, in term of conclusion, we can say that we have not enough information about the problem to ask the question. We have to know the range of feasibility (constraint RHS - allowable decrease; constraint RHS + allowable increase) to decide what constraint is more interesting to double In this slide 16 will find a network composed of nodes and arcs. [...]

[...] were two types of constraints: productions' constraints and purchase's constraints. The mean shrewdness of this case is to name E production' units and A', B', C', D', E' purchasing' units in order to differentiate sources of units and constraints related in the same time. d. Reallocating vehicles This case was a problem of re-distribution. The decision variable was how many bikes we need to move from X to Y (with a total of 8 different bike' stations). The objective was to minimize transportations cost. [...]

[...] Table II- Original report of sensibility analysis Adjustable Cells Final Reduced Objective Allowable Allowable Cell Name Value Cost Coefficien Increase Decrease t Constraints Final Shadow Constraint Allowable Allowable Cell Name Value price RHS Increase Decrease Thanks to this sensibility analysis report, we can see allowable increase and allowable decrease for each product and each ingredient. c. Analysis of changes with Objective Functions coefficient Table III Optimal solution obtain by solver changing OF Coefficient (cell B C Used Availabl e n I have to produce the same quantity of bread and croissant dough than in the original model even if the maximum profit increase. [...]

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