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
