Transcript Chapter 2 Basic Concepts

Chapter 2
Basic Concepts
Fundamental Statistics for the
Behavioral Sciences, 5th edition
David C. Howell
©2003 Brooks/Cole Publishing Company/ITP
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Chapter 2 Basic Information
Major Points
• Scales of measurement
• Variables
• Random sampling
• Notation
• Review questions
Chapter 2 Basic Information
Scales of Measurement
• Definition
• Nominal scales
• Ordinal scales
• Interval scales
• Ratio scales
• What does it all mean?
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Chapter 2 Basic Information
Variables
• Define variable
 Property of an object or event that can take on
different values
• Discrete variable
 Variable that can take on only a small set of possible
values
• Continuous variable
 Variable that can take on any value
Cont.
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Chapter 2 Basic Information
Variables--cont.
• Independent variables
 Those variables controlled by the
experimenter
• Dependent variables
 Those variables being measured
 The data or score
Chapter 2 Basic Information
Random Sampling
• Define
• Distinguish between random sampling
and random assignment
• How to draw a random sample
 A big hat
 Random number tables
 Why not just make them up in your head?
• A class demonstration
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Chapter 2 Basic Information
Notation
• Variable names
 X and Y
• Individual values
 Xi
• X versus Xi
• Summation notation
 X
 X2
 (X)2
 XY
 X Y
 Constants
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Chapter 2 Basic Information
Hypothetical data on family size by decade of 20th century
Decade
(X)
3
Family
Size(Y)
5.2
X2
9
Y2
27.04
X–Y
-2.2
XY
15.6
4
4.8
16
23.04
-0.8
19.2
5
3.5
25
12.25
1.5
17.5
6
2.5
36
6.25
3.5
15.0
7
2.3
49
5.29
4.7
16.1
25
18.3
138
73.87
6.7
83.4
Chapter 2 Basic Information
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Review Questions
• Give an example of a nominal, ordinal,
interval, and ratio scale.
• What kinds of scales would apply to
hours of sunlight and quality of life?
• Why is random assignment more
important than random sampling?
Cont.
Chapter 2 Basic Information
Review Questions--cont.
• Why are X2 and (X)2 different?
• What happens when you multiply by a
constant, or add a constant?
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