Chapter 1: Research
Methods
Psychological Research
• Scientific Observation: A systematic empirical
investigation that is structured to answer
questions about the world
• Research Method: Systematic approach to
answering scientific questions
Correlations
• Existence of a consistent, systematic
relationship between two events, measures,
or variables
Correlation
Perfect positive
correlation (+1.00)
No relationship (0.00)
Perfect negative
correlation (-1.00)
Scatterplots, showing patterns of correlations
Correlation
95
Temperament 90
scores 85
80
75
70
65
60
55
50
45
40
35
30
25
55
60
65
70
Height in inches
75
80
Scatterplot of Height and Temperament
85
Positive Correlation
• Increases in one measure are matched by
increases in the other measure
Negative Correlation
• Increases in one measure are matched by
decreases in the other measure
Coefficient of Correlation
• Statistical index ranging from -1.00 to +1.00
that indicates direction and degree of
correlation
– Closer the statistic is to –1.00 or to +1.00,
the stronger the relationship
– Correlation of 0.00 demonstrates no
relationship between the variables
Correlation and Causation
• Correlation does not demonstrate causation:
Just because two variables are related does
NOT mean that one variable causes the other
to occur
Naturalistic Observation
• Observing a person or an animal in the
environment in which the person or animal
lives
Limitations
• Observer Effect: Changes in a subject’s
behavior caused by an awareness of being
observed
• Observer Bias: Occurs when observers see
what they expect to see or record only
selected details
• Anthropomorphic Error: Attributing human
thoughts, feelings, or motives to animals,
especially as a way of explaining their
behavior (e.g., “Anya my cat is acting like that
because she’s feeling depressed today.”)
The Survey Method
• Using public polling techniques to answer
psychological questions
• Representative Sample: Small group that
accurately reflects a larger population
– Population: Entire group of animals or
people belonging to a particular category
(e.g., all married women)
• Courtesy Bias: Problem in research; a
tendency to give “polite” or socially desirable
answers
The Clinical Method
• Case Study: In-depth focus of all aspects of a
single subject
• Natural Clinical Tests: Natural events, such
as accidents, that provide psychological data
Experiments
• A formal trial to confirm/disconfirm a
hypothesis and to identify cause and effect
relationships
The Scientific Method
• Six Basic Elements
– Observing
– Defining a problem
– Proposing a hypothesis (an educated
guess that can be tested)
– Gathering evidence/testing the hypothesis
– Publishing results
– Building a theory
Hypothesis
• Predictable outcome of an experiment or an
educated guess about the relationship
between variables
• Operational Definition: States exact
procedures used to represent a concept.
Allows abstract ideas to be tested in realworld terms
Performing an Experiment
• Directly vary a condition you might think
affects behavior
• Create two or more groups of subjects, alike
in all ways except the condition you are
varying
• Record whether varying the condition has any
effect on behavior
Variables
• Any condition that can change and that might
affect the outcome of an experiment
Independent Variable
• Condition(s) altered by the experimenter;
experimenter sets their size, amount, or
value. These are suspected causes for
behavioral differences
Dependent Variable
• Measures the results of the experiment;
Condition is affected by independent variable
Extraneous Variables
• Conditions that a researcher wants to prevent
from affecting the outcomes of the experiment
(e.g., number of hours slept before the
experiment)
Groups
• Experimental Group: The group of subjects
that gets the independent variable
• Control Group: The group of subjects that
does NOT get the independent variable
• Random Assignment: Subject has an equal
chance of being in either the experimental or
control group
Placebo
• A fake pill (sugar) or injection (saline)
• Placebo Effect: Changes in behavior that
result from expectations that a drug or other
treatment will have some effect; the belief that
one has taken an active drug
Experiment Types
• Single Blind: Only the subjects have no idea
whether they are in the experimental or
control group
• Double Blind: The subjects AND the
experimenters have no idea whether the
subjects are in the control or experimental
group
– Best type of experiment if properly set up
Experimenter Effects
• Changes in subjects’ behavior caused by the
unintended influence of the experimenter’s
actions
• Self-Fulfilling Prophecy: A prediction that
leads people to act in ways to make the
prediction come true
Assessing Experiments
 Reliability
 the extent to which a test yields consistent
results
 assessed by consistency of scores on:
 two halves of the test
 alternate forms of the test
 retesting
 Validity
 the extent to which a test measures or
predicts what it is supposed to
Statistical Reasoning
 Mode
 the most frequently occurring score in a
distribution
 Mean
 the arithmetic average of a distribution
 obtained by adding the scores and then dividing
by the number of scores
 Median
 the middle score in a distribution
 half the scores are above it and half are below it
Statistical Reasoning
A Skewed Distribution
15 20 25 30 35 40 45 50
90
475
70
Mode Median
One Family
Mean
Income per family in thousands of dollars
710
Assessing Intelligence
 Standardization
 defining meaningful scores by comparison
with the performance of a pretested
“standardization group”
 Normal Curve
 the symmetrical bell-shaped curve that
describes the distribution of many physical
and psychological attributes
 most scores fall near the average, and fewer
and fewer scores lie near the extremes
Normal Distribution
The Normal Curve
Statistical Reasoning
 Range
 the difference between the highest and lowest
scores in a distribution
 Standard Deviation
 a computed measure of how much scores vary
around the mean
 Statistical Significance
 a statistical statement of how likely it is that an
obtained result occurred by chance
Variance and Standard Deviation
• SD= √variance
• What does this mean?
Critical Thinking
• Ability to analyze, evaluate, compare, critique,
and synthesize information
Ethics in Psychology
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Informed consent
Debrief
Protection of Participants
Deception
Confidentiality
Withdrawal from Experiment