The Nuts and Bolts of Quasi-Experiments Chapter 12 The Nuts and Bolts of Quasi-Experiments Dawn M. McBride The Process of Research in Psychology Second Edition

Steps in the Research Process Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Quasi-Experiments A type of research design where a comparison is made, as in an experiment, but no random assignment of participants to groups occurs Pretest-Posttest designs Time series designs Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Quasi-Experiments Behaviors fore which random assignment would be difficult, impossible or unethical. Field settings: Schools, mental health agencies Parenting behaviors Quality of Therapists Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Pretest-Posttest Designs No control group: compare post-test with pre-test scores May include control group, without random assignment: non-equivalent groups Implement a new intervention with one classroom of 8th graders and use another classroom as control If random assignment is used– then study is an experiment (pre-test may be used or not) Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Pretest-Posttest Designs Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Sources of bias: History effects- Regression towards the mean events that occur during the course of a study to all or individual participants that can result in bias. 9-11 Hurricane Regression towards the mean Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Pretest-Posttest Designs: Bias Testing effects Possible solution Solomon four-group design (Shadish et al., 2002). one set takes the pretest and posttest one set that takes only the posttest Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Pretest-Posttest Designs Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Time Series Designs Measuring the behavior or attitude multiple times before and event or ttreatment and multiple times after over the same time period. The patterns of scores over time before and after the event or treatment are compared to determine if a difference has occurred. Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Time Series Designs: Interrupted The “treatment” is an independent event, such as a historical event. Iraq war Patterns of scores are compared over time: before and after the event occurs Typically uses archival data: e.g. Consumer confidence Index; Census Data Requires sophisticated data analyses procedures Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

FDA warning Oct 2013 antidepressants and suicide risk Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Noninterrupted Time Series Designs The “treatment” is implemented by the researcher The participants’ depression symptoms would be measured over a period of time before they began the new therapy after therapy concludes Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Noninterrupted Time Series Design Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.

Times Series D. Sources of Bias History recession, natural events Maturation changes that occur to the participants during the course of a study that can result in bias Developmental changes Attrition Dawn M. McBride - The Process of Research in Psychology, 2nd Edition © 2013 SAGE Publications, Inc.