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International Hellenic University Paraskevopoulos Konstantinos
1
E x e r c i s e Decision Trees
1 In this Exercise • Build a Decision Tree • Decision nodes • Event nodes • End nodes • Calculate expected values
Duration : 80 minutes
Decision Scenario NiceCeramics A.E. is the biggest ceramic tile producer in Greece and one of the greatest in Europe.
The main factory of the company, located in Thessaloniki, is producing annually 5.500.000 m² of tiles,
whereas 45% of its production is being exported to 34 countries all around the world.
The Vice President of the company Grigoris Keramidas expressed his wish for your opinion on a
decision the company must make during the next days, so he recruited you as a consultant to make a
recommendation.
During a meeting, Keramidas expressed his worry to you, for a new competitor company
MoreniceCeramics. This new competitor has entered the Greek market during the last year and is
now openly threatening the primacy of NiceCeramics in sales in Greece. The headache for
NiceCeramics started when MoreniceCeramics have launched a very successful series of floor tiles for
internal and external use, which are cheaper and better quality than existing tile series of
NiceCeramics. Keramidas explains to you that NiceCeramics needs to develop a new product and
face the threat. The design department of the company has come up with two product ideas, and
gave them the code names Supertile and Saviortile. The production of the new product has to start as
soon as possible, so NiceCeramics has resources and time to develop only one of the two products or
none of them. The Business Analysis department of NiceCeramics says that Supertile product will cost
90.000€ to develop, and if it succeed it will generate a revenue of 900.000€. On the other hand, the
analysts of the Business Analysis department believe that Saviortile product will cost only 9.000€ to
develop with a generated revenue of 250.000€ if it will succeed.
Your task is to help Mr. Keramidas to decide which product, if either, to develop. You have to use a
decision tree to describe and then to evaluate the decision alternatives, given all the uncertainties
involved, in a measurable way. If you succeed a promotion is waiting for you!
Decision Trees
Solution using DETRETU software A decision tree is a way to describe an algorithm that helps identify a strategy most likely to reach a
goal. It uses diagrams of nodes and connecting branches. These diagrams contain nodes that indicate
decision points, chance events or branch terminals and are read from left to right. Branches
correspond to each decision alternative or event outcome emerging from a node.
The first decision node (root node)
You can start building your first decision tree in DETRETU, by following the next steps:
1. Select File > Create new Decision Tree. A new node will be inserted in the canvas area of the
application window as shown in Figure 1. This node will be the root node of your decision tree.
The root node will play the role of a decision node and will represent the first set of decision
alternatives. While executing the following steps, your tree will start expanding to the right.
Figure 1
2. For each decision alternative add a branch, extending to the right from the root node. To do that
click on the triangle shape on the right side of the root node. On the dialog frame Insert New
Branch (Figure 2) that will show on your screen select Decision Node and click OK. This action
will result in adding two new nodes at the right side of the root node. Repeat the same steps to
add one more decision node in the root node. Your tree should look like Figure 3 now.
Figure 2
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Decision Trees
Figure 3
International Hellenic University 3
look like the one is shown in Figure 4
4. node Supertile insert the number ‐90000 e clicking on the label with the number 0.00
3. Rename the three new nodes by clicking on the name label of each one of them. Rename the
one on the top to Supertile, the one in the middle to Saviortile and the one at the bottom to
Neither. Your tree now should .
Figure 4
In by doubl
under the label with the name Supertile. This number is the associated investment cost to
develop Supertile. Note that this cost is a negative value since it represents loss of money. Do
the same with the node Saviortile by inserting the number ‐9000, as this is the investment cost
to develop this product. Leave the node Neither intact, as there is no investment cost if the
company decide to invest in none of the two products. Your tree now should look like the one in
Figure 5.
Figure 5
Paraskevopoulos Konstantinos
Decision Trees
Event nodes and outcome probability
Each product development effort in NiceCeramics decision scenario can have one out of two
outcomes. Each plan for developing a new product can either succeed or fail. In the following steps
you will insert in the decision three those perspectives.
1. Click on the triangle shape on the right side of the Supertile node to open the dialog frame
Insert New Branch as shown in Figure 2.
2. Select the graphic Event Node and then click OK to insert two event nodes on the right side
of node Supertile. Those two new nodes depict the two possible outcomes of developing
Supertile product. The one at the top represents success and the other failure. Label the two
branches accordingly. The result should be similar as the one shown in Figure 6.
Figure 6
Note the percentage numbers in front of each one of the two new nodes. Those percentages
are the chances that each event node has to happen. The program by default sets each one
of those percentages in 50%.
3. Repeat step two to insert two new nodes at the right side of Saviortile node. Your tree
should now look like the one shown in Figure 7.
4. You can now incorporate the relative outcome probability, or uncertainty, associated with
each chance event. The Business Analysis department of NiceCeramics gave you the
information that the Supertile has a 50% chance of success and 50% chance of failure. The
Saviortile has 70% chance of success, and therefore 30% chance of failure. Insert those
values by double clicking on the percentage field of each event node. Your decision tree
should look like the one shown in Figure 8.
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Decision Trees
Figure 7
Figure 8
End nodes
Now it’s time to insert at the end nodes the values that represent the cash flow for each one of
them. The logic is similar as before, when you entered the nodes Supertile and Saviortile. Then you
had to depict the investment cost for both products, by typing the investment values as negative
numbers in both nodes. Now you will have to do the same with the ending nodes. According to
NiceCeramics scenario if Supertile product succeeds then the generated revenue for the company
5 International Hellenic University Paraskevopoulos Konstantinos
Decision Trees
will be 900.000€. On the other hand if Saviortile product succeeds then the generated revenue for
the company will be 250.000€. To depict those revenues in your decision tree, do the following steps:
1. Double click the label with the number 0.00 in the Supertile Success node and type the
number 900000, as this is the expected generated revenue in case of success in investing in
Supertile product.
2. Do the same with the Saviortile Success node and type the number 250000, as this is the
expected revenue incase of successful investment in product Saviortile.
Note that you should leave both Failure nodes with zero values as in case of a failure in
investment there is no revenue or extra lose other than the amount of money depicted with
the negative values in the nodes Saviotile and Supertile.
Your decision tree now should look like the one in Figure 9.
Figure 9
Congratulations! You just finished building your first decision tree. In the next step you are going to
find out which one (or neither) of the two alternative products Supertile or Saviortile to produce.
6 International Hellenic University Paraskevopoulos Konstantinos
Decision Trees
Final answer
In this step you are going to evaluate the relative merits of each decision alternative. The way to
combine payoffs and probabilities for each node is called Expected monetary value (EMV). The higher
the EMV, the better a particular decision alternative on average, when compared to the other
alternatives in the decision tree.
The calculations needed to find the best path, in other words the most profitable product to develop
in the decision tree can be made automatically from DETETRU, by clicking the menu Tree > Solve. In
Figure 10 you can see the result of such an action. The best path is colored black whereas the other
paths are colored light gray color.
Figure 10
Let’s see now how DETRETU came up with the conclusion that the Supertile project is the best to
follow. Let’s see how you would make all the calculations by hand if you didn’t have DETRETU.
First you would need to calculate the EMV in end nodes. You can calculate the EMV in end nodes by
finding the total profit or lose in each one of the paths. For example the EMV in the first node
Success (child node of Supertile) is 810.000€ as the total profit of this path is 900.000 – 90.000€.
Using the same logic the EMV of node Failure (the child node of Supertile) is ‐90.000. Do the same
calculations for the other end nodes to find all the EMVs.
Second you would need to calculate the EMVs for any event node by summing together all the EMVs
for each branch that is connected to the node. The general formula for calculating EMV at any
chance nodes is given as:
7 International Hellenic University Paraskevopoulos Konstantinos
Decision Trees
International Hellenic University Paraskevopoulos Konstantinos
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…
In NiceCeramics scenario, if the Supertile product is successful, the EMV is the profit multiplied by its
probability, thus 810.000· 50% = 405.000. On the other hand if the Supertile product fails, the EMV
is 90.000 · 50% = 45.000. The EMV for the decision to develop the Supertile product, incorporating
both success ailure is of EM the ev and f the sum V for all entualities.
405.000 45.000 = 360.000
Similarly, the EMV for the decision to develop the Saviortile is given by 241.000 70%
9000 30% 168.700 2.700 166.000 .
Third in row, you would have to calculate the EMVs for the root decision node. The EMV for this
node is calculated by calculating the maximum EMV from the children nodes. As you can see in
Figure the maximum EMV from the three nodes Supertile, Saviortile and Neither is the EMV 360.000
from node Supertile. Now you can report the analysis with these summarized presentation points:
• The Supertile is a better product to develop, despite the great risk. The significantly larger
anticipated profits make the risk more acceptable than the Saviortile product.
• The Saviortile product is less risky to develop, but also significantly less profitable. The
project does not overcome the expected value of its rival project, bearing in mind the given
profit expectations.