Types of Experimental Designs
• Non-experimental
– Post-test only
– Pre-post test
• Experimental
–
–
–
–
Pre & post-test with control group
Pre & multiple post-test with control group
After-only control group
Solomon four-group
• Quasi
– Non-equivalent control group
– Simple time-series
– Multiple time series
Laboratory vs. Field Experiments
• Lab
– Artificial (Low external validity)
– Control of variables (High internal validity)
– Good for theory building and process-level
understanding
• Field
– Realistic (High external validity)
– Less control (Low internal validity)
– Good for program evaluation
Non-Experimental
• No control group
• No measurement of dependent variable
before intervention
• Referred to as quasi-experiment in
Sekaran
Non-Experimental
• Post-test only
–
–
–
–
Referred to as quasi-experiment in Sekaran
Measurement taken only after intervention
No baseline measure taken
Hard to determine if change
• has occurred
• is due to intervention
– Good for studying nature of intervention
– Useful for evaluating participant learning after a
training session
Intervention
Post-measure
Non-Experimental
• Pre-test/post-test
– Referred to as quasi-experiment in
Sekaran
– Change inferred from differences in pre vs.
post intervention measures
Pre-measure
Intervention
Post-measure
Non-Experimental
• Pre-test/post-test
– Is affected by testing, instrumentation,
history, time, maturation, & statistical
regression effects
– Use internal referencing data to test
whether only relevant var changed and
irrelevant var did not change following
intervention
Pre-measure
Intervention
Post-measure
Experimental
• Control group
• Random assignment of participants to
conditions
– Is the study described in the ethnic identity
paper (Kim & Gelfand) an experiment? Why
or Why not?
Experimental
• Pre-test/post-test w/control group
Experimental group
Pre-measure
Intervention
Pre-measure
Control group
• Subject to mortality threats
Post-measure
Post-measure
Experimental
• Pre-test/post-test w/control group (omnibus
test= repeated measures anova)
– Experimental group should be ‘better’ than
control group on post-test measures (t-test
independent groups)
– Experimental group scores should “improve”
from pre to post-test (t-test paired)
– Control group scores should not change from pre
to post-test (t-test paired)
– Should be no group differences on pre-test
measures esp on matching variables if random
assignment was not possible (t-test independent
groups)
Experimental
• Pre-test & Post-test Control Group with
multiple post-test measures
Experimental group
Pre-measure
Pre-measure
Intervention
Post-measure 1,2,3
Post-measure 1,2,3
Control group
– Tests long and short term effects of
intervention (e.g., training)
Experimental
• Pre-test & Post-test Control Group with
multiple post-test measures (adapted to
org’n stakeholders’ needs)
Experimental group
PreIntervention
measure
PreControl
measure
Control group
Post-measure 1
Post-measure 1
Control
Intervention
Postmeasure 2
Postmeasure 2
Experimental
• After only control group
Experimental group
Control group
Intervention
Post-measure
Post-measure
• Eliminates testing effects found in pre-test post-test
control group design
• Classified as quasi-experimental in Sekaran
• Referred to as post-tests only with experimental &
control groups in Sekaran
• Subject to Selection & mortality threats
Experimental
• Solomon Four-group design
Experimental group
Pre-measure
Intervention
Post-measure
Control group
Pre-measure
Experimental group
Control group
Post-measure
Intervention
Post-measure
Post-measure
Copyright © 2003 John Wiley & Sons, Inc. Sekaran/RESEARCH 4E
TABLE 7.2
Types of Experimental Designs
• Experimental
– Pre & post-test with control group
– Pre & multiple post-test with control group
– After-only control group
– Solomon four-group
• Quasi
– Non-equivalent control group
– Simple time-series
– Multiple time series
Quasi-Experimental
• Non-equivalent control group
– E.g., training conditions assigned to preexisting groups
– Gather pre-intervention data on important
control variables.
– Use pre-measure as a statistical control in
the analyses for differences in postintervention measures
Quasi-Experimental
• Simple time-series design
Pre-measure 1, 2, 3
Intervention
Post-measure 1,2,3
• Pre-measures should not be different from
each other
• Post measures should not be different from
each other
• Pre vs. post measures should be different
from each other
Quasi-Experimental
• Multiple time-series design
Pre-measure 1, 2, 3
Intervention
Post-measure 1,2,3
Experimental group
Pre-measure 1, 2, 3
Post-measure 1,2,3
Control group
• Same conditions as simple time series design plus..
• Pre and post measures of control group should
not differ from each other
• Limitations: Testing effects, instrumentation
problems
Types of Experimental Designs
• Non-experimental
– Post-test only
– Pre-post test
• Experimental
–
–
–
–
Pre & post-test with control group
Pre & multiple post-test with control group
After-only control group
Solomon four-group
• Quasi
– Non-equivalent control group
– Simple time-series
– Multiple time series