1. Experimental Designs

2. Campbell & Stanley’s (1963) three general types of experimental designs
Pre-experiments
Quasi-experiments
Full or true experiments

3. Key concepts
Random assignment: assigning participants to the various conditions in an experiment to achieve equivalent groups for comparison purposes.
Treatment condition: administering the experimental manipulation
Control condition: no experimental manipulation or an alternative, benign manipulation
Pretest: measurement of the dependent variable(s) prior to exposure to a treatment or control condition
Posttest: measurement of the dependent variable(s) following the treatment or control conditions.

4. notation for experimental designs
R = random assignment
01 = pre-test (measurement)
02 = post-test (measurement)
X1 = treatment, stimulus condition, or manipulation
X0 = control group (no treatment)

5. PRE-EXPERIMENTAL DESIGNS
one-shot case study: A group (usually intact) is administered a treatment and then measured or observed. No attempt is made to randomly assign subjects to condition, nor does the design provide for any additional groups as comparisons.
(no random assignment) X1 O1
one group, pre-test, post test design (no random assignment) O1 X O2
static group comparison: only one of two intact groups is given the experimental treatment. At the end of the treatment, both groups are observed or measured to see if there is a difference between them as a result of the treatment.
(no random assignment) X1 01
X0 01
PRE-EXPERIMENTAL DESIGNS

6. Quasi-experimental designs
Pre-test, post-test, quasi-equivalent groups design
(no random assignment) X O2 O2
Times-Series design

7. FULL EXPERIMENTAL DESIGNS
pre-test/post-test equivalent groups design R 01 X O2
01 O2
post-test only equivalent groups design R T O1 O1
Solomon four-group design R 01 X O O2
X O2 O2
FULL EXPERIMENTAL DESIGNS

8. true/full experimental designs
Solomon Four Group design: attempts to control for the possible "sensitizing" effects of the pre-test or measurement by adding two groups who have not been a part of the pre-test or pre-measurement process.
R 01 X1 O O2
X1 O2 O2

9. Factorial designs (may be full or quasi-experimental)
Advantage: Allows the researcher to uncover interaction effects
2 X 2 design
Two independent variables
Two levels/values per variable
Four conditions being compared
3 X 2 X 2 design
Three independent variables
Three levels/values for one independent variable, two levels/values for the other two independent variables
Twelve conditions being compared