NW
Lecture 1
Material Covered in This Lecture:
Chapter 1, Section 1.1: Displaying Distributions with Graphs.
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1. Definitions (Introduction, p.46)
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(1). Individuals are the objects described by a set of data.
(2). Variable: A variable is any characteristic of an individual. A
variable can take
different values for different individuals
Example: A college's student data base includes data about every currently
enrolled student. The students are the individuals described by
the data set. For each individual, the data contain the values of
variables such as date of birth, gender, choice of major, and
grade point average (GPA). The following is a small part of
the data set in MINITAB.
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3). Classification of Variables
Categorical Variable
: A categorical variable places an individual into
one of several groups or categories.
Example: Gender, Major, Blood type, etc.
Quantitative Variable
: A quantitative variable takes numerical values for
which arithmetic operations such as adding and averaging make sense.
Example: Weight, Height, etc.
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2. Displaying Distribution with Graphs. (Section 1.1, p.724)
Exploratory data analysis:
Investigate the rough, basic structure of the
data. Two basic strategies to organize the exploration of a set of data:
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h Begin by examining each variable by itself. Then move on to
study the relationships among the variables.
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h Begin with a graph or graphs. Then add numerical summaries
of specific aspects of the data.
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 Summer '08
 NANE
 Frequency, Histogram

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