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
N = no 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.
N X1 O1
one group, pre-test, post test design N 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.
X1 01 N
intact groups, no pretest N X0 01

6. Quasi-experimental designs
Pre-test, post-test, quasi-equivalent groups design
N X O2
N O2
Times-Series design N

7. Full Experimental Designs
pre-test/post-test equivalent groups design R 01 X1 O2
01 O2
post-test only equivalent groups design R X1 O1 O1
Solomon four-group design R 01 X1 O O2
X1 O2 O2
a.k.a. two-group posttest only design

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