The Basics of Experimentation Flashcards
The _______ involves the manipulation of variables to establish cause-and-
effect relationships. The key features are controlled methods and the random assignment
of participants into controlled and experimental groups.
experimental method
are interested in exploring theoretical questions, often by
creating a hypothesis and then setting out to prove or disprove it through experimentation.
use scientific methods to collect data and perform research.
Some researchers have devoted their entire career to answering one complex research
question
Experimental psychologists
a manipulation of the
environment controlled
by the experimenter
in the sense that its values are created by the experimenter
and are not affected by anything else that happens in the experiment
Independent
Variable
response measure of
an experiment that is
dependent on the
subject
Dependent
Variable
Advantages
of an
Experiment
Better control of extraneous
variables
Permits statements about
causation
Economy
Why Experiments
are Conducted
- In basic research, experiments are performed to test
theories and to provide a database for explanations of
behavior. - To repeat or replicate a previous finding
- To demonstrate cause-and-effect relationships
- To solve problems and validate results
try to pit two theories against each other to
make different predictions
the experiment will determine which theory to
reject and which to keep
Critical Experiments
performed in the absence of a compelling
theory just to see what happens
require no knowledge of theory or the existing
database, and can be formulated on the basis
of personal experience and observations
What-if Experiments
at least 2 conditions must be compared with each other to determine if
the IV produces a change in behavior or outcome
these 2 levels might simply be the presence or absence of a manipulation
before an experiment can be established, IV with at least 2 levels are
necessary
Levels of the IV
failure of an IV to control behavior: can have more than one interpretation
The experimenter may have guessed incorrectly that the IV was
important.
The experimenter may not have created a valid manipulation of the
IV
Null Results
does not receive the levels of interest of the IV
provides a baseline against which some variable of interest can be
compared
Control Group/Control Condition
one criterion for a good DV is
stability
The purpose of _______ is to minimize extraneous variables or
uncontrolled variation, thereby increasing the likelihood that an experiment
will produce valid, consistent results
Experimental
Designs
every participant experiences only one
condition, and you compare group differences
between participants in various conditions
Between- Subjects Design
Between- Subjects Design is considered_____ - because there is
no chance that one treatment will continue to
contaminate the other, because each person
receives only one treatment
conservative
administer a test before the experiment
to obtain a baseline
baseline scores could be used to form
pairs of subjects that had equal or very
similar scores
Equivalent Groups
each person participating in an
experiment has an equal chance of
being assigned to any group
Randomization
an experimental design method wherein all
participants are exposed to every condition of
the independent variable
Within-
Subjects
Design
Within- Subjects Design also known as ______
many experimenters prefer this
more efficient, since each subject is compared
with himself or herself
can be helpful when resources are limited or
when investigating the real-world effects of
treatments or programs
repeated measures design
taking part in different levels of the
treatment or taking the measurement tests
several times might help the participants
become more skilled
control by:
randomizing task order - to avoid
patterns where everyone improves on
later tasks
General Practice Effects
the effect of the early part of the experiment
on the later part of the experiment varies
depending on which treatment comes first
can be controlled through counterbalancing
used to control for any effect that the
order of presenting stimuli might have on
the dependent variable
ex: presenting tasks in a different order to
different participants
complete counterbalancing - makes
sure that all possible treatment orders are
used
in addition: build a sufficient time delay
between the two treatments
Differential Carryover Effects
- makes
sure that all possible treatment orders are
used
complete counterbalancing
participants may become exhausted,
bored, or less motivated after taking part in
multiple treatments or tests
control by:
designing the experiment as short as
possible without losing important data
give participants regular breaks
make the tasks interesting or
interactive
shuffle the order of the tasks so the
most important ones aren
’t always at
the end when people are tired
Participant Fatigue
variant of within-subjects design
presents the levels of the IV or treatments to a
small number of subjects or a single subject
available population may be small
internal validity is often very good - no
individual differences
external validity is a problem
Small n Design
utilizes a three-stage process that includes:
A - baseline measurement
B - treatment
A - withdrawal
ABA Design
A -
B -
A -
baseline measurement
treatment
withdrawal
have some IVs treated as between-subjects
and others as within subjects in the same
experiment
not as efficient or economical as a pure within-
subjects design, but it is often safer
Mixed
Design
Major Types of Extraneous Variables
01Physical Variables
02 Social Variables
03 Personality Variables
factors in an experimental setting that are unrelated to the research
variables but can still influence the outcome of the experiment
physical elements in the environment or conditions that could affect
‘participants
performance, behavior, or responses, potentially introducing
unwanted variation or bias into the study
aspects of the testing conditions that need to be controlled
Examples: day of the week, testing room, noise, external distractions
PHYSICAL
VARIABLES
Control
Techniques
A. Elimination
B. Constancy
C. Balancing
.
a method used to control physical extraneous
variables in an experiment by removing or
eliminating the potential influence of those
variables
If the noise might confound the results, test in a
quiet location.
If you do not want interruptions, hang a sign on
the door saying,
“Do not disturb. Experiment in
”progress.
However, not all physical variables can be
controlled
Elimination
keeping all aspects of treatment conditions as
nearly similar as possible
if we cannot eliminate an extraneous variable,
we try to make sure that it stays the same in all
treatment conditions
keep the mechanics of the testing procedures
uniform as well
Constancy
The goal is to ensure that the
extraneous factors are evenly distributed
across all experimental conditions. minimizing
their potential impact on the result
Balancing
external social factors that can unintentionally influence the outcome of the
study, making it harder to establish a clear cause-and-effect relationship
between the independent and dependent variables
qualities of the relationships between subjects and experimenters that can
influence results
SOCIAL
VARIABLES
aspects of the experimental situation that demand that people behave in a
particular way
Demand Characteristics
Controlling
Demand
Characteristics
a. Single-Blind Experiment
b. Cover Stories
participants do not know which group they
are in (experimental or control) or what the
true purpose of the study is, but the
researcher knows
We can disclose some but not all
information about the experiment to
subjects
Common in experiment with drugs
placebo effects
Single-Blind Experiment
Common in experiment with drugs
placebo effects
plausible but false explanation for the
procedures used in the study
told to disguise the actual research
hypothesis so that subjects will not guess
what it is
has to give the subjects an explanation for
what we want them to do without tipping
them off to the hypothesis being tested
Cover Stories
when the researcher
’
s expectations or behavior subtly influence
participant’
s responses
the experimenter could give a cue to respond in a particular way or might
behave differently in different treatment conditions
Experimenter Bias
Experimenter Bias
experimenters might also treat subjects differently depending on what they
expect from them
______
Rosenthal Effect
Controlling
Experimenter
Bias
a. Double-Blind Experiment
b. Standardize the Instructions
subjects do not know which treatment they
are receiving, and the experimenter does
not know either
If the experimenter does not know which
treatment treatment the subject is getting,
he or she cannot bias the responses in any
systematic way. The subject is kept in the
dark, too, so the effects of demand
characteristics are controlled along with
experimenter bias
a. Double-Blind Experiment
ensures that the researcher does not
unintentionally influence participants
through tone, wording, or additional
explanations
every participant receives identical
instructions, making the experiment easier to
replicate with consistent results
Standardize the Instructions
can arise from both the experimenter and the subjects,
potentially affecting the outcome of an experiment
PERSONALITY
VARIABLES
An experimenter who is warm and friendly can elicit very different
responses from subjects than can one who is cold and aloof.
Experimenter
extent to which someone or something is admired or considered
valuable in a social group
the tendency of individuals to present themselves in a manner that will
be viewed favorably by others
Social Desirability
Controlling
Personality
Variables
(Subjects)
a. Random Assignment
b. Keep face-to-face contact to a minimum
Controlling
Personality
Variables
(Experimenter)
a. Maintain consistency in interactions with
subjects.
b. If possible, use multiple experimenters.
c. Keep face-to-face contact to a minimum
and always adhere strictly to the
experimental procedures
The more you vary your behavior, the more
you are likely to produce variability in the
responses of your subjects. The more
variability in their responses, the harder it
will be to detect the effect of the
independent variable.
Maintain consistency in interactions with
subjects.
