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Research methods
Zhuanghua Shi
Scientific research cycles
questions
Using right format & Style
Research
report
Using right
methods
Validate it
using scientific
methods
Literature
research
Hypothsis
Using right
tools and right
reading
behavior
Research methods
Descriptive Method– to describe the nature of
situation and to explore the causes
Experimental Method - one variable is
manipulated while another variable is observed
and measured. Used to establish cause-andeffect relationship between variables
Descriptive Research
Ways of obtaining descriptive information
Asking participants to provide information
e.g. Interview
Observation
Communication between investigator and participants
Activity Analysis: actual behavior of the participants
Situation analysis: determines the sets of conditions in which
the behavior of the participant occur.
Types of Descriptive
Research
Case studies
E.g. a special patient
Study in depth
Be aware: lack of generality Surveys
Gathering data from a relative large samples
Determining variables rather than about
individuals
Random sample Be aware: Unrepresentative samples (internet surveys?)
order of questions (order effects), response
options, and the wording of questions
Types of Descriptive
Research
Developmental studies
Reliable information that deals with the
progress or stages of development of an
individual
Investigating a progression
Methods
Longitudinal method: Study of participants
over an extended period of time
Cross-section method: Study of participants in
different level and focus on characteristics
Types of Descriptive
Research
Follow-up studies
To investigate the subsequent development of
participants after a specified treatment or
condition
Documentary analysis
Content analysis
Gathering information by examining records
and documents
Types of Descriptive
Research
Correlational analysis
To determine the extent to which different
variables are related to each other. e.g., # of hours of media exposure to violence
& level of aggression
e.g., certain illness and optimism/pessimism
To estimate a relationship (distinguished from
simple descriptive methods)
Be aware: Correlation ≠ Causation
Advantages/Disadvantages of descriptive method
Advantages
All information is gathered
It can be applied to a broad range of studies
Disadvantages
Any method has its own limits, be aware of this
Tend to avoid statistical analysis, merely
information gathering
Variables under study are hardly controlled.
Example of descriptive method
Mashmallow experiment
http://www.youtube.com/watch?v=6EjJsPylEOY
Experimental method
Experimental
Psychology
Industrial
Psychology
Social
Psychology
Developmental
Psychology
Experimental
methods
Applied
Psychology
Clinical
Psychology
Educational
Psychology
Experimental methods
Used to examine cause-and-effect relationships
Cause
effect
Two essential characteristics:
Researcher has control over the experimental
procedures to make sure that everything (but the
variable being manipulated) stays the same.
Researcher manipulates one variable by changing its
value from one level to another. A second variable is
observed (measured) to determine whether the
manipulation causes changes to occur
Participants are randomly assigned to different
treatment conditions (they cannot self select).
Example: Hermann Grid illusion
Manipulate variable: ?
Example: Scintillation
Compared to classical Hermann Grid illusion, which variable has been
manipulate: ?
Variables
Independent Variable (IV)
variable that we expect causes an outcome
the antecedent event
variable that the experimenter can control and
manipulate
Dependent Variable (DV)
the “effect”
the outcome variable
it’s value depends on the changes introduced by
the IV
Extraneous (Confounding) Variables
Potential source of error in an experiment; must be
held constant across conditions
Independent variables and Conditions
Must have at least two conditions (also called “levels”)
of the IV in order to demonstrate that the IV has an
effect on the DV. Otherwise, it wouldn’t be a
‘variable’.
Experimental condition (IV present) vs. control
condition (IV not present)
Those in control condition receive no treatment or
receive neutral, placebo treatment. Provides
baseline for comparison with experimental
condition.
Example
Curvature of Hermann Grid
Experimental condition - curvature
Baseline condition – linear grid
Dependent variables
Out come effects
Behavioral responses
Yes/No (perceived or not)
Multiple choices
Rating (confidence)
Saccades
Neurophysiological measures
Continuous output (EEG, MEG measures)
pupil dilations
Heart beats etc.
Extraneous (Confounding) Variables
In reality, there are many other factors (variables),
which may influence on the results (outcomes) –
confounding variables
They influences the validity of the experiment
Experimental bias
Experimental Bias
Experimental Bias
When an investigator has certain expectations
about the outcome of an experiment, these
expectations may contaminate the entire
experience.
Incentive / motivation
The experimenter can subtly alter his or her
behavior in carrying out the experiment in a
number of ways and so produce biased results,
such as instruction
As fast as possible vs. As accuracy as possible
Control experimental bias
Placebo control
Placebo effect: provides no active effect
Use in identical conditions for control and
experimental groups
Blind experiment
Researchers blind to group membership of
participants to rule out experimenter bias
Strongest experiments – double blind design
Researchers and participants kept blind
Control experimental bias
Double blind Experiment
Control other factors
Laboratory Experiments
Experimental environments
E.g., temperature, ambient light in room
Same setting: viewing distance etc.
Participants
Age, sex, visual acuity (balanced)
Randomization
Morning / Afternoon
Control other factors
Field Experiments
Conducted in real-world
Advantage
People are more likely to act naturally
Disadvantage
Experimenter has less control (“quasiexperiments”)
Quasi-independent variable Typically something the experimenter cannot
manipulate such as gender or smoking
Control methods
Balance the survey using large samples(gender,
sex)
Using different days
Control other factors:
Groups
Within-subject design
All participants
exposure to all
conditions
Randomization
Within-subject
comparison
Between-subject
design
Experimental group
vs. control group
Patient studies
Random
assignment
Sex, age,
education should
be balanced
Theory and hypothesis
Theory
A set of statements designed to explain a set
of phenomena
more encompassing than a hypothesis
Hypothesis
A statement, usually designed to be tested by
an experiment that tentatively expresses a
cause-and-effect relationship with variables.
Operational definition
What Makes a Good Theory?
Incorporates existing facts
It is testable
Predictions made by the theory are supported
by the findings of new studies
It conforms to the law of parsimony
From Theory to Testable Questions
Operational Definition
A specific, observable response that is used to
measure a concept
Validity – the ability of a test to measure what it
was designed to measure. Are we really measuring what we say we are?
Reliability – the repeatability of a measurement. Basically, the extent to which the measurement
device yields the same approximate results when
utilized repeatedly under the same conditions.
Constructs & Operational Definitions
Empirical Realization
translating the conceptual or abstract variables
contained in your hypothesis to real,
measurable constructs
constructs – abstract level
operational definition The specific way in which a construct is
manipulated or measured
Examples
Crusco & Wetzel (1984)
interested in how touching influences individuals’
perceptions of others
description of study
waitress performed normal duties
when she gave change to customer, she
approached the paying customer from the side,
leaned forward, and w/out making eye contact, said
in a friendly yet firm tone, “Here’s your change.”
1/3 – no touch control condition
1/3 – a brief hand-touch condition
1/3 – a longer shoulder-touch condition
left a blank survey for customers to complete
collected survey and tip
Examples
Crusco & Wetzel (1984)
IV: nature of physical contact
DV: ratings of waitress on Questionnaire
and amount of tip
Touch has a positive effect on tipping behavior. When patrons are
touch by a waiter or a waitress, they became more generous and left
a higher tip.
Examples
The effects of mood on helping (Isen & Simmonds,
1978, Social Psychology, v41)
researchers go to shopping malls and set up
observation near phone booths. Their participants are individuals who use the
phone booths when the vicinity is otherwise
unoccupied. For half of the Ps, the researchers leave a quarter
to be found near the booth. For all of the Ps, when
the phone call is completed and the person leaves
the telephone booth, a confederate walks by the
booth, and drops a file folder full of papers. The researchers watch to see if the Ps help pick
up the dropped papers.
Examples
Constructs
IV: Mood
DV: Helping
Operational
IV: finds a quarter
DV: help pick up paper
Putting people in a good mood leads them to be more helpful.
Examples
Researchers are interested in the
interference effects (Stroop effect)
of font color on word naming task.
They use the words as shown on the
right. Participants are instruct to name the
word as quick as possible,
meanwhile they should avoid their
errors.
ORANGE
BLUE
GREEN
YELLOW ORANGE
GREEN PURPLE
GREEN
BLACK YELLOW
Examples
Stetson, Fiesta, & Eagleman, 2007, Does Time
Really Slow Down during a Frightening Event?
Abstract level: ?
Operational level:
?
Summary: Research
methods
Descriptive method
case studies, survey, developmental study, followup study, documentary analysis, correlation analysis
Experimental method
variables and conditions
Experimental biases
Theory and hypothesis
construct operational definition
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