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PSYCH202A: Research Methods

Unit 4: Measurement Concepts   All research measures something and that “something” is a variable. This unit will provide an in-depth introduction to variables and approaches to measuring them. Variables are not always as tangible in psychology as they are in other disciplines (i.e., in psychology, you may be attempting to measure someone’s happiness, whereas in medicine, you might be measuring someone’s weight). As such, psychologists have had to develop certain tools and methodologies in order to accurately and reliably gather data. In this unit, we will learn the ways in which psychologists measure their findings and the terms they commonly use to evaluate the quality of such measurement.

Unit 4 Time Advisory
This unit should take approximately 9 hours to complete.

☐    Subunit 4.1: 2 hours

☐    Sub-subunit 4.1.1: 0.5 hours

☐    Sub-subunit 4.1.2: 0.5 hours

☐    Sub-subunit 4.1.3: 0.5 hours

☐    Sub-subunit 4.1.4: 0.5 hours

☐    Subunit 4.2: 3 hours

☐    Sub-subunit 4.2.1: 1 hour

☐    Sub-subunit 4.2.2: 1 hour

☐    Sub-subunit 4.2.3: 1 hour

☐    Subunit 4.3: 3 hours

☐    Sub-subunit 4.3.1: 2 hours

☐    Sub-subunit 4.3.2: 0.5 hours

☐    Sub-subunit 4.3.3: 0.5 hours

☐    Subunit 4.4: 1 hour

Unit4 Learning Outcomes
Upon successful completion of this unit, the student will be able to:
- List and define the four levels of measurement. - Define operational definition. - Define reliability and the four main types of reliability. - Define validity and compare and contrast reliability and validity. - Define internal and external validity and compare and contrast these two types of validity. - Define construct validity, face validity, predictive validity, concurrent validity, convergent validity, and discriminant validity. - List and define the nine threats to internal validity and the four threats to external validity.

4.1 Variables   4.1.1 What is a Variable and Why is it Important?   - Reading: Research Methods Knowledge Base: William Trochim’s “Variables” Link: Research Methods Knowledge Base: William Trochim’s “Variables” (HTML)

 Instructions: Measurement involves variables. Please read this
webpage to review the types of variables. This will serve as a
refresher before we begin.  

 Reading this webpage should take approximately 30 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above. The Saylor Foundation is grateful to
Professor William Trochim for his kind permission to reference
students to this site.

4.1.2 The Independent Variable versus the Dependent Variable   - Reading: AllPsych Online: Dr. Christopher Heffner’s “Chapter 7.2: Variables” Link: AllPsych Online: Dr. Christopher Heffner’s “Chapter 7.2: Variables” (HTML)

 Instructions: This reading will allow you to review the difference
between independent and dependent variables. Measurement issues will
apply to dependent variables.  

 Reading this webpage should take approximately 30 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

4.1.3 Levels of Measurement and Measurement Scales   - Reading: Research Methods Knowledge Base: William Trochim’s “Levels of Measurement” Link: Research Methods Knowledge Base: William Trochim’s “Levels of Measurement” (HTML)

 Instructions: Please read this webpage to learn about levels of
measurement and measurement scales. Because the different
measurement scale types will affect the kind of analysis that you
can do with the data, it is important to be able to identify the
measurement scale used by a particular study’s dependent variable.
At the end of this subunit, you should be able to list and define
the four levels of measurement.  

 Reading this webpage should take approximately 30 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above. The Saylor Foundation is grateful to
Professor William Trochim for his kind permission to reference
students to this site.

4.1.4 Operational Definition of a Variable   - Reading: Dr. Russell A. Dewey’s “Operational Definitions”, “Operational Definitions: Not Always ‘Good’”, and “Distinguishing Operational Definitions, Variables, and Values” Link: Dr. Russell A. Dewey’s “Operational Definitions” (HTML), “Operational Definitions: Not Always ‘Good’” (HTML), and “Distinguishing Operational Definitions, Variables, and Values” (HTML)

 Instructions: Before we can manipulate or measure a variable, we
must define it. These definitions are in terms of the operations
performed. So, for measurement, the operational definition specifies
the operations performed to measure a variable. Please read these
webpages to learn about operational definitions. At the end of this
subunit, you should be able to define the term *operational
definition* and compare and contrast effective and less effective
operational definitions.  

 Reading these webpages should take approximately 30 minutes (about
10 minutes each).  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpages above.

4.2 Reliability   4.2.1 What is Reliability and Why is It Important?   - Reading: Research Methods Knowledge Base: William Trochim’s “Theory of Reliability” Link: Research Methods Knowledge Base: William Trochim’s “Theory of Reliability” (HTML)

 Instructions: It is important for measures to be reliable
(consistent over time). Even though the source for this subunit is
somewhat technical, please read this webpage for an introduction to
the concept of reliability. At the end of this subunit, you should
be able to define the term *reliability* and describe what it means
for a variable to have low or high reliability.  

 Reading this webpage should take approximately 1 hour.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above. The Saylor Foundation is grateful to
Professor William Trochim for his kind permission to reference
students to this site.

4.2.2 Types of Reliability   - Reading: Research Methods Knowledge Base: William Trochim’s “Types of Reliability” Link: Research Methods Knowledge Base: William Trochim’s “Types of Reliability” (HTML)

 Instructions: Even though reliability refers to consistency, there
are a number of ways for this to be realized. Please read this
webpage for an overview of the different types of reliability. This
reading will cover interrater (interobserver) reliability,
test-retest reliability, parallel-forms reliability, and internal
consistency reliability (including split-half reliability and
Cronbach’s alpha). At the end of this subunit, you should be able to
define the four main types of reliability.  

 Reading this webpage should take approximately 1 hour.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above. The Saylor Foundation is grateful to
Professor William Trochim for his kind permission to reference
students to this site.

4.2.3 The Difference between Reliability and Validity   - Reading: Research Methods Knowledge Base: William Trochim’s “Reliability & Validity” Link: Research Methods Knowledge Base: William Trochim’s “Reliability & Validity” (HTML)

 Instructions: This subunit serves as a bridge between the concepts
of reliability and validity. Reliability refers to how consistent a
measurement is. Validity refers to whether the measurement is
measuring the thing you think it is measuring. Please read this
webpage for a review of reliability and validity and the differences
between them and a discussion of how they are interrelated. At the
end of this subunit, you should be able to define validity and
compare and contrast reliability and validity.  

 Reading this webpage should take approximately 1 hour.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above. The Saylor Foundation is grateful to
Professor William Trochim for his kind permission to reference
students to this site.

4.3 Validity   4.3.1 What is Validity and Why is it Important? Internal and External Validity   - Reading: Research Methods Knowledge Base: William Trochim’s “Introduction to Validity”, “Internal Validity”, and “External Validity” Link: Research Methods Knowledge Base: William Trochim’s “Introduction to Validity” (HTML), “Internal Validity” (HTML), and “External Validity” (HTML)

 Instructions: Please read the first page for an introduction to the
concept of validity. Please read the second two pages for a
definition of internal and external validity and to gain an
understanding of what distinguishes internal validity from external
validity. At the end of this subunit, you should be able to define
internal validity and external validity. You should also be able to
distinguish internal from external validity.  

 Reading these webpages should take approximately 2 hours (about 1
hour for the first one and 30 minutes each for the second and
third).  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpages above. The Saylor Foundation is grateful
to Professor William Trochim for his kind permission to reference
students to this site.

4.3.2 Types of Construct Validity: Content Validity, Face Validity, Predictive Validity, Concurrent Validity, Convergent Validity, and Discriminant Validity   - Reading: Research Methods Knowledge Base: William Trochim’s “Construct Validity” Link: Research Methods Knowledge Base: William Trochim’s “Construct Validity” (HTML)

 Instructions: Construct validity assesses whether your measuring
instrument is measuring the thing it is intended to measure. Please
read the above webpage in order to understand the concept of
construct validity. Please also click the link for “measurement
validity types” and read that page to learn about the different ways
to assess construct validity. At the end of this subunit, you should
be able to define construct validity and identify the main issue in
assessing construct validity. You should also be able to define face
validity, predictive validity, concurrent validity, convergent
validity, and discriminant validity.  

 Reading this webpage should take approximately 30 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above. The Saylor Foundation is grateful to
Professor William Trochim for his kind permission to reference
students to this site.

4.3.3 Threats to Validity of Research Designs   - Reading: Chong-ho Yu and Barbara Ohlund’s “Threats to Validity of Research Design” Link: Chong-ho Yu and Barbara Ohlund’s “Threats to Validity of Research Design” (HTML)

 Instructions: It is important to evaluate the validity of research
designs carefully. This is true of research that you are conducting,
but it is also important to be an educated consumer of research
produced by others. Please read through the first two sections of
this webpage (“Problem and Background” and “Factors Jeopardizing
Internal and External Validity”) for an overview of threats to
validity. You may stop at “Three Experimental Designs.” At the end
of this subunit, you should be able to list and define the nine
threats to internal validity and the four threats to external
validity. These lists will be helpful as you read research
reports.  

 Reading this webpage should take approximately 30 minutes.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.

4.4 Assessment: Measurement Concepts   - Assessment: California State University, Fullerton: Paul Cozby’s “Measurement Concepts” Link: California State University, Fullerton: Paul Cozby’s “Measurement Concepts” (HTML)

 Instructions: After you have completed Unit 4, please take the
above assessment to test your knowledge.  

 Completing this assessment should take approximately 1 hour.  

 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above.