Chapter 10:
Decision Trees
157
CHAPTER TEN:
DECISION TREES
CONTEXT AND PERSPECTIVE
Richard works for a large online retailer. His company is launching a next-generation eReader
soon, and they want to maximize the effectiveness of their marketing. They have many customers,
some of whom purchased one of the company’s previous generation digital readers. Richard has
noticed that certain types of people were the most anxious to get the previous generation device,
while other folks seemed to content to wait to buy the electronic gadget later. He’s wondering
what makes some people motivated to buy something as soon as it comes out, while others are less
driven to have the product.
Richard’s employer helps to drive the sales of its new eReader by offering specific products and
services for the eReader through its massive web site—for example, eReader owners can use the
company’s web site to buy digital magazines, newspapers, books, music, and so forth. The
company also sells thousands of other types of media, such as traditional printed books and
electronics of every kind. Richard believes that by mining the customers’ data regarding general
consumer behaviors on the web site, he’ll be able to figure out which customers will buy the new
eReader early, which ones will buy next, and which ones will buy later on. He hopes that by
predicting when a customer will be ready to buy the next-gen eReader, he’ll be able to time his
target marketing to the people most ready to respond to advertisements and promotions.
LEARNING OBJECTIVES
After completing the reading
and exercises in this chapter, you should be able to:
Explain what decision trees are, how they are used and the benefits of using them.
Recognize the necessary format for data in order to perform predictive decision tree
mining.
Data Mining
for the Masses
158
Develop a decision tree data mining model in RapidMiner using a training data set.
Interpret the visual tree’s nodes and leaves, and apply them to a scoring data set in order
to deploy the model.
Use different tree algorithms in order to increase the granularity of the tree’s detail.
ORGANIZATIONAL UNDERSTANDING
Richard wants to be able to predict the timing of buying behaviors, but he also wants to
understand how his customers’ behaviors on his company’s web site indicate the timing of their
purchase of the new eReader. Richard has studied the classic diffusion theories that noted scholar
and sociologist Everett Rogers first published in the 1960s. Rogers surmised that the adoption of
a new technology or innovation tends to follow an ‘S’ shaped curve, with a smaller group of the
most enterprising and innovative customers adopting the technology first, followed by larger
groups of middle majority adopters, followed by smaller groups of late adopters (Figure 10-1).
Figure 10-1. Everett Rogers’ theory of adoption of new innovations.
Those at the front of the blue curve are the smaller group that are first to want and buy the
technology. Most of us, the masses, fall within the middle 70-80% of people who eventually
acquire the technology. The low end tail on the right side of the blue curve are the laggards, the
ones who eventually adopt. Consider how DVD players and cell phones have followed this curve.
Understanding Rogers’ theory, Richard believes that he can categorize his company’s customers
into one of four groups that will eventually buy the new eReader: Innovators, Early Adopters,
Early Majority or Late Majority. These groups track with Rogers’ social adoption theories on the
diffusion of technological innovations, and also with Richard’s informal observations about the
speed of adoption of his company’s previous generation product. He hopes that by watching the
Number of adopters by group
Cumulative number of adopters
over time