True Experiments
All true experiments must have what three things?
Manipulation, randomization which give control
In an experiment, the manipulated variable is
An advantage of a between-subjects design is
only one observation is needed
In quasi-experiments, different groups or conditions are defined in terms of
pre-existing participant variables or time
Nonequivalent groups means
Groups that are not equal or similar
Also: researcher has no control over who is in which group - groups occur naturally or are pre-existing
How are true experiments different from other types of research?
Only true experiments can demonstrate cause-and-effect relationships between variables.
Any variable that exists within a study other than what is being studied is called
an extraneous variable
Between-subjects is different from Within-subjects in that in a between-subjects design
uses a different group of participants for each treatment condition
Quasi-experiments are most often conducted in what settings?
Academic, clinical, or other real-world settings
A nonexperimental design involving one group of participants measured before and after a treatment
O X O
A procedure in which a random process is used to assign participants to treatment conditions is called
random assignment (a key characteristic of a true experiment)
A variable that varies systematically with the treatment conditions and might influence participants' scores is called
a confounding variable
In between-subjects designs, the separate groups must be as
similar as possible in all ways except the manipulated variable
(participant characteristics, environmental variables, time)
A quasi-experimental design involving multiple measurements of one group before a treatment and then again after treatment
O O O X O O O
Time-Series Design
How much control does the researcher have over extraneous variables or random assignment in a nonexperiment?
No control. There is no manipulation of variables and no random assignment to groups. Everything occurs naturally.
The specific treatment conditions that are used in an experiment are called
the levels of the independent variable
A variable that is used to create groups, but cannot be manipulated ethically or logistically is called
Which design involves measuring the same group of participants in two or more treatment conditions?
Within-subjects
What distinguishes a quasi-experiment from a nonexperiment?
The amount of control. A quasi-experiment has some control over variables and looks like a true experiment, but cannot provide one clear answer or show cause-and-effect.
Which research design compares preexisting groups differing in age?
Cross-sectional Developmental Design
(Nonexperimental, Nonequivalent groups, developmental design)
What are the three main ways to control confounding variables?
Matching and Randomization
A confounding variable is unacceptable in an experiment because
An advantage of a within-subjects design is
only one group of participants is needed
What is often added to a nonexperiment to make it a quasi-experiment?
Control in the form of a pretest (Pretest-Posttest nonequivalent control group design) or more observations which serve as a baseline (Time-series design)
What distinguishes a cross-sectional developmental design from a longitudinal developmental design?
Longitudinal studies compare one group of participants over a long, long period of time.