125
T
EACHING
S
UGGESTIONS
Teaching Suggestion 10.1:
Transportation Models in the Chapter.
This is a long chapter, in part, because of the four transportation
algorithms that are discussed. If time is an issue in your course, se
lect one of the two initial solution methods and one of the two
Fnal solution methods to cover in class. The easiest, but
not
most
efFcient, are the northwest corner and steppingstone rules.
Teaching Suggestion 10.2:
Using the Northwest Corner Rule.
This approach is easily understood by students and is appealing to
teach for that very reason. Make sure the students understand the
weakness of the algorithm (that is, it ignores costs totally). Ask
them to come up with their own approaches that could improve on
this. Invariably, a good student will present an approach that
comes very close to VAM. Name the student’s approach after him
(or her) and tell him he could have been famous if he had devised
it 50 years earlier.
Teaching Suggestion 10.3:
Using the SteppingStone Method.
Students usually pick up the concept of a closed path and learn to
trace the pluses and minuses fairly quickly. But they run into prob
lems when they have to cross over an empty cell. Stress that the cities
in the tableau are just in random order, so crossing an unoccupied
box is Fne. The big test is Table 10.5. Once students comprehend
this tracing, they are usually ready to move on. Remind students that
there is
only one
closed path that can be traced for each unused cell.
Teaching Suggestion 10.4:
Dummy Rows and Columns.
Another confusing issue to students is whether to add a dummy
row (source) or dummy column (destination) in a transportation
problem. A slow and careful explanation is valuable so that stu
dents can reach an intuitive understanding as to the correct choice.
Also note that the software adds these dummies automatically.
Teaching Suggestion 10.5:
Handling Degeneracy in
Transportation Problems.
Just as a warning, be aware that students are often confused by the
concept of where to place the zero so that the closed paths can be
traced. Carefully explain why you chose or didn’t choose a certain
cell. The choice of cell can affect the number of iterations that fol
low.
Teaching Suggestion 10.6:
Facility Location Problems.
These are an important application of the transportation model and
make it easy to compare how a new city will Ft into an existing
shipping network. It is an application that has intuitive appeal.
Both QM for Windows and Excel QM software are easy to run on
these problems.
Teaching Suggestion 10.7:
Sensitivity Analysis on the
Assignment Problem.
This algorithm is easy to use and understand. Tell about solving a
large stafFng problem, then discuss the cost implications if one
worker is not available or insists on doing a particular task. It is
easy, with the software, to recompute the answers and conduct a
sensitivity analysis. This is the basis of Problem 1037.
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 Spring '11
 MichaelHanna
 The Land, Assignment Models, CH10 GGS

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