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Chapter 4

Chapter 4 Textbook Notes

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Anna Nagy

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Chapter 4
oA variable is any event, situation, behaviour, or individual characteristic
that varies
oE.g. cognitive task performance, word length, spatial density, intelligence,
gender, reaction time, rate of forgetting, aggression, speaker credibility,
attitude change, anger, stress, age, self-esteem
Each of these variables represents a general class w/in which specific
instances will vary
These specific instances are called the levels or vales of the variable
oMust have 2 or more levels or values
oSome variables will have numeric values hence they will be quantitative (ie.
Age, your IQ). They differ in amount or quantity. Algebra can be applied to
such variables (ie. Measure the mean)
oSome variables are not numeric and instead identify categories hence they
are categorical (ie. Gender, occupation). These variables differ, but not by
quantity, and algebra cannot be applied to them
oClassified into 4 general categories
Situational variables
Describe characteristics of a situation or environment
The length of words that you read in a book, the spatial density
of a classroom, the credibility of a person who is trying to
persuade you, the number of bystanders to an emergency
Response variables
The responses or behaviours of individuals
Reaction time, performance on a cognitive task, helping a
victim in an emergency
Participant or subject variables
Individual differences, characteristics of individuals
Including gender, intelligence, personality traits such as
Mediating variables
Psychological processes that mediate the effects of a situational
variable on a particular response
Operational Definitions of Variables
oA definition of the variable in terms of the operations or techniques the
researcher uses to measure or manipulate it
oCognitive task performance may be operationally defined as the number of
errors detected on a proofreading task during a 10 minute period
oThere also may be several levels of abstraction when studying a variable

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A variable such as word length is concrete and easily operationalized
in terms of numbers of letters or syllables, the exact words of the study
must still be selected
oOperationally defining variables causes researchers to discuss abstract
concepts in concrete terms, a process that can lead to the realization that the
variable is in fact too vague to study. This doesnt mean the concept is
useless, but systemic research is not possible until the concept can be
operationally defined.
oOperational variables also help us communicate our ideas to others. For
example, when someone is talking about aggression, you need to know exactly
what is meant by aggression because there are many ways of operationally
defining it.
oThere are a variety of methods to operationally define variables, each with
advantages and disadvantages. Researchers must decide on the best one to
use given the problem of study, goals of research, ethics, etc.
oBecause no one method is perfect, understanding a variable entirely involves
studying the variable in a variety of operational definitions.
Relationships Between Variables
oThe relationship between two variables is the general way in which the
different values of one variable are associated with the different values of
another variable. That is, do the levels of two variables vary systematically
o4 most common relationships found in research
Positive linear relationship
Increases in the values of one variable are accompanied by
increases of the second variable
E.g. height/weight
Negative linear relationship
Increases in the values of one variable are accompanied by
decreases in the values of the other variable
E.g. time studying/grades
Curvilinear relationship
Increases in the values of one variable are accompanied by both
increases and decreases in the values of the other variable
The direction of the relationship changes at least once
Sometimes referred to as a nonmonotonic function
E.g. the amount of money spent on advertising by a
company/the profit of that company
No relationship
Flat line, variables are independent of each other
oThe positive and negative relationships described are examples of
monotonic relationships the relationship between the variables is always
positive or always negative

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oFigure 4.2 on page 72 illustrates a positive monotonic relationship that is not
strictly linear
oIt is also important to know the strength of the relationship between two
variables. That is, we need to know the size of the correlation between the
oCorrelation Coefficient the numerical index of the strength of a
relationship between variables
oStrong correlation two variables are strongly related and there is little
deviation from the general pattern
oWeak correlation two variables are not strongly related because many
individuals deviate from the general pattern
Relationships and Reduction of Uncertainty
oWhen we detect a relationship between variables, we reduce uncertainty of
the world by increasing our understanding of the variables we are examining
oThe term uncertainty implies that there is a randomness in events; scientist
refer to this as random variability or error variance in the events that occur
in the world
oAsk 200 students if they like shopping, 100 said yes, 100 said no
This variability is called random or error variance, called error b/c we
dont understand it
If you walked up to anyone at your school and tried to guess whether
the person likes shopping, you would have to make a random guess—
you would be right half the time and wrong half the time, if we could
explain the variability it would no longer be random
So how can random variability be reduced? By identifying the
relationship between the variables
Reduce by gender, how you would be right a higher % of time
oThe relationship between variables is stronger when there is less random
Nonexperimental Vs. Experimental Methods
oNonexperimental method
Relationships are studied by making observations or measures of the
variables of interest
Behaviour is observed as it occurs naturally
May be done by asking people to describe their behaviour, directly
observing their behaviour, recording physiological responses,
examining various public records such as census data
A relationship b/w variables is established when the 2 variables vary
E.g. students who work more hours have a lower grades
oExperimental method
Involves direct manipulation and control of variables
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