Psychological
Research &
Statistics
Chapter 20
Objectives
 Describe
the process of psychological
research
 Name the different types of psychological
research and some of the
methodological hazards of doing
research
 Describe descriptive & inferential statistics
 Name specific research methods used to
organize data
Key terms
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Case study
Central
tendency
Control group
Correlation
Correlation
coefficient
Cross-sectional
studies
Dependent
variable
Descriptive
statistics
Experimental
group
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
Frequency
distribution
Histogram
Independent
Variable
Inferential
statistics
Longitude
studies
Mean
Median
Mode
Naturalistic
observation
Normal curve
Population
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Range
Sample
Self-fulfilling
prophecy
Standard
deviation
Statistics
Survey
Validity
Variable
Variance
APA CODE of ETHICS
1.
2.
Informed Consent
Protect subjects from harm
1.
2.
3.
4.
5.
Psychological
Physical
Subjects can withdraw anytime
Debriefing
Subjects anonymous
What do you think?
 Amazing
Randi
Gathering Data
 How
do psychologist collect information
about the topic they’ve chosen to study?

Social psychologist who is studying the
effects of group pressure is likely to conduct
an experiment

A psychologist who is interested in
personality theories might begin with
intensive case studies of individuals

Whatever the approach, decision must be made
in advance
Gathering Data: VALIDITY

Stop hair loss

“Freedom from wrinkles”

Huge weight lose in “just 2 weeks!”

Self-help books: (How to achieve the perfect relationship)

Actors playing experts

Task of psychologists is to determine validity:


Validity: The ability of a test to measure what it is intended to
measure; verifying a theory
A theory cannot be accepted until it has been repeatedly
tested
Gathering Data: SAMPLES

A psychologists wants to know how the desire
to get into college affects the attitudes of
high-school juniors and seniors.


Would it be possible to test all in the country?
What would the psychologist do?

Sample: The small portion of data, out of the
total amount available, that a researcher
collects

Population: The total group of subjects from
which a sample is drawn
Gathering Data: SAMPLES

Choosing a sample may be tough!

Samples must be representative of the
population a researcher is studying

Ex: If you wanted to know how tall American
men are, what professional group would you
make certain not to have a disproportionately
large number of representatives?


NBA basketball players
If you didn’t what would this sample be?

Biased, it would not represent American men in
general
Gathering Data: SAMPLES

How to avoid a biased sample?

Take a purely random sample


To ensure that each individual within the scope of
the research has an equal chance of being
represented
How?


Choose every 20th name on school enrollment lists
Deliberately pick individuals who represent the
various subgroups in the population being
studied

How?

Research on students, select students of both sexes,
varying ages, of all social classes, from all neighborhoods
(Stratified sample)
Gathering Data:
CORRELATIONS & EXPLANATIONS
 Examine
a relationship between two sets
of observations

EX: Students grades & number of hours they
sleep
 Correlation:
The degree of relatedness
between two sets of data
Gathering Data:
CORRELATIONS & EXPLANATIONS

What would be the correlation between IQ scores
and academic success?
High IQ tend to go with high grades
 Low IQ tend to go with low grades


Negative correlation


Smoking cigarettes and living long, healthy life
Student example of correlations?
Experiments
 Why
would a researcher choose
experimentation over other research
methods?

Experimentation enables the investigator to
control the situation and to decrease the
possibility that unnoticed, outside factors
will influence the results
 What

is an experiment designed to do?
Prove or disprove a hypothesis
Experiments

Variables: In an experimental situation, any
factor that is capable of change

2 types of variables

Independent: In an experiment, the factor that is
deliberately manipulated by the experimenters
to test its effect on another factor; the cause of
change

Dependent: The factor, chosen by the
experimenter, that may or may not change
when the independent variable is changed
Experimental Method
 Worksheet

Independent & Dependent variable
Experiments
 Experimental
group: The group of subjects
to which an independent variable is
applied

Is there a chance that subjects will act
differently because it is an experiment?
 Controlled
group: Group who is treated in
the same way as the experimental group,
except the experimental treatment
(independent variable) is not applied
Experiments
 What

is necessary in all experiments?
Control group
 What
would happen without a control
group?

Researcher cannot be sure the
experimental group is reacting to- a
change in the independent variable
Worksheet
 Thinking
Drunk, Driving Drunk
 Marriage:
Practice Makes Imperfect
Naturalistic Observation
 Researchers
need to understand the way
people & animals behave naturally.

Naturalistic observation: Studying
phenomena as they occur in natural
surroundings, without interfering
Naturalistic Observation
 Examples




Psychologists might join a commune
Take position behind a 2-way mirror to
watch youngsters play
Live in the jungle to study behavior of
gorillas (Gorillas in the Mist)
CARDINAL RULE of Naturalistic Observation:

Avoid disturbing the people or animals you are
studying
Walk on the Wild Side!
 This
is the way we walk
Case Studies
 Case
study: An intensive investigation of
an individual or group, usually focusing on
a single psychological phenomenon
 Value

of case studies?
Provide a wealth of descriptive material
that may generate new hypotheses that
researchers can then test under controlled
conditions with comparison groups
New York University
 Investigate
the psychological
characteristics of people receiving death
 15
inmates
 Are
death row inmates shrewd, cold
killers?
New York University
 Findings



All 15 had history of severe head injury
12/15 showed signs of brain damage
Most are below average IQ
Surveys
 Survey:
Sampling of data, obtained
through interviews and questionnaires
 May
be impersonal, but most practical
way to gather data on the attitudes,
beliefs, and experiences of large numbers
of people
Surveys
Advantages
Disadvantage
May gather a lot of
information on the attitudes,
beliefs, and experiences of
large numbers of people
Impersonal
Who responds?
Wording of questions
Low response rate
90% of people surveyed
said…
Interviews
 Studying
people face to face and asking
questions
Advantages
Disadvantages
Get detailed personal
information
Interviewer bias
Interviewees fact from
fiction
Longitudinal Studies
 Longitudinal
Studies: Repeatedly
gathering data on the same group of
subjects over a period of time for the
purpose of studying consistencies and
changes
 Has
behavior or feelings changed?
Cross-sectional Studies

Alternative approach to gathering data is
Cross-sectional study: Acquiring comparable
data subgroups on the basis of certain criteria
for the purpose of studying similarities and
differences

Ex: Give an IQ test to individuals 30,40, & 60
years old and compare average scores, then
draw conclusions about intelligence at
various ages
Cross-sectional Studies

Advantages:



Less expensive
Reduce amount of time needed for study
Disadvantage

With the previous example with IQ and age
Example concluded that intelligence declines
with age, but age may not be the primary
cause of decline
 What could have influenced the results?


Education, life experiences, opportunity
Avoiding Errors in doing
Research
 Self-fulfilling
prophecy: A belief,
prediction, or expectation that operates
to bring about its own fulfillment
 How
to avoid self-fulfilling prophecy is to
use the double-blind technique
Avoiding Errors in doing
Research

Single-blind technique



Wants to study the effects of a tranquilizer
One group receives the drug
Other group receives a placebo (harmless
substitute for the drug)

Which group is experimental & controlled?

Next step to compare performances on a series of
tests

Who is blind in this experiment?
Avoiding Errors in doing
Research
 How
could we make the previous
experiment a double-blind experiment?

Both the researcher and the subjects do
not know who took the drugs or the
placebo

Eliminates the possibility that the researcher
will unconsciously find what she expects to
find about the effects of the drug
Avoiding Errors in doing
Research
 Psychologists
are like you and I, they have
attitudes, feelings, and ideas of their own,
and their reactions to different subjects
may distort the results of a study.
 Researchers
may unknowingly react
differently to male and female subjects,
short and tall subjects, subjects who speak
with an accent
Avoiding Errors in doing
Research
 What
would happen if several children
being studied in a play area were
introduced to a television camera man
and said they were going to be on TV
tonight?
Statistical Evaluation
 How
many times have you been told that,
in order to get good grades, you have to
study? A psychology student named Jolly
Mames has always restricted the amount
of TV she watches during the week,
particularly before a test. She has a friend
though who does not watch TV before a
test but who still does not get good
grades. This fact challenges Jolly’s belief.
Statistical Evaluation

Jolly hypothesizes that, among her
classmates, those who watch less TV get
better grades, she decides to conduct a
survey to test the validity of her hypothesis.

Asks 15 students in her class to write down
how many hours of TV they watch the night
before their weekly psychology quiz and how
many hours they watched on the night after
the quiz.
Statistical Evaluation

Jolly collect addition information like
checking off familiar products on a list of20
brand name items that were advertised on TV
the night before the quiz. Jolly also asks her
subjects to give their height

Data is turned in and Jolly is overwhelmed
with the amount of information she has
collected
Statistical Evaluation

How can it be organized so it will make
sense?

How can Jolly analyze it to see whether it
supports or contradicts her hypothesis?

Statistics: The branch of mathematics
concerned with summarizing and making
meaningful inferences from collections of
data
Before
After
Grade (10 highest possible)
Products
Height
0.0
1.5
5
2
71
0.5
2.5
10
4
64
0.5
2.5
9
6
69
1.0
2.0
10
14
60
1.0
2.5
8
10
71
1.0
1.5
7
9
63
1.5
3.0
9
7
70
1.5
2.5
8
12
59
1.5
2.5
8
9
75
1.5
3.0
6
14
60
2.0
3.0
5
13
68
2.5
2.5
3
17
65
2.5
3.5
4
10
72
3.0
3.0
0
18
62
4.0
4.0
4
20
67
Statistical Evaluation
How
much television did
the two students with the
best grades watch the
night before the quiz?
Before
After
Grade (10 highest possible)
Products
Height
0.0
1.5
5
2
71
0.5
2.5
10
4
64
0.5
2.5
9
6
69
1.0
2.0
10
14
60
1.0
2.5
8
10
71
1.0
1.5
7
9
63
1.5
3.0
9
7
70
1.5
2.5
8
12
59
1.5
2.5
8
9
75
1.5
3.0
6
14
60
2.0
3.0
5
13
68
2.5
2.5
3
17
65
2.5
3.5
4
10
72
3.0
3.0
0
18
62
4.0
4.0
4
20
67
Descriptive Statistics

When the study is complete, the first task is to
organize the data in as brief and clear a
manner as possible.

Jolly must put her responses together in a
logical format. When she does she will be
using

Descriptive statistics: The listing and
summarizing of data in a practical, efficient
way, such as graphs and averages
Descriptive Statistics
 Distributions
of data:

One of the 1st steps is to organize their data
is to create frequency tables and graphs.

Tables and graphs provide a rough picture
of the data (initial peek of data)
 Are
scores bunched up or spread out?
 What scores occur most often?
Descriptive Statistics

Jolly is interest in how many hours of TV her
subjects watched the night before and the
night after the quiz.

Jolly uses the numbers of hours of TV viewing
as categories and then she counts how many
subjects reported each category of hours
before and after the quiz.

Jolly has created a table

Frequency distribution: An arrangement of data
that indicates how often a particular score or
observation occurs
Jolly’s Frequency Table
Hours
Frequency Before
Frequency After
0.0
1
0
0.5
2
0
1.0
3
0
1.5
4
2
2.0
1
1
2.5
2
6
3.0
1
4
3.5
0
1
4.0
1
1
Total
15
15
Quiz: Understanding Research
 Video