Chapter 7EXPERIMENTAL DESIGNS

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

Intervention Post-measurePre-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

Intervention Post-measurePre-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

Intervention Post-measurePre-measure

Post-measurePre-measure

Experimental group

Control group

• Subject to mortality threats

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)

• Pre-test & Post-test Control Group with multiple post-test measures

Experimental

Intervention Post-measure 1,2,3Pre-measure

Post-measure 1,2,3Pre-measure

Experimental group

Control group

– Tests long and short term effects of intervention (e.g., training)

• Pre-test & Post-test Control Group with multiple post-test measures (adapted to org’n stakeholders’ needs)

Experimental

Intervention Post-measure 1Pre-measure

Experimental group

Control group

Control Post-measure 2

Control Post-measure 1Pre-measure Intervention Post-

measure 2

Experimental• After only control group

Intervention Post-measure

Post-measure

Experimental group

Control group

• 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

• Solomon Four-group design

Experimental

Intervention Post-measurePre-measure

Post-measurePre-measure

Experimental group

Control group

Intervention Post-measure

Post-measure

Experimental group

Control group

TABLE 7.2Copyright © 2003 John Wiley & Sons, Inc. Sekaran/RESEARCH 4E

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 pre-existing groups

– Gather pre-intervention data on important control variables.

– Use pre-measure as a statistical control in the analyses for differences in post-intervention measures

• Simple time-series design

Quasi-Experimental

Intervention Post-measure 1,2,3Pre-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

• Multiple time-series design

Quasi-Experimental

Intervention Post-measure 1,2,3Pre-measure 1, 2, 3

Post-measure 1,2,3Pre-measure 1, 2, 3Control group

Experimental 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