PSY 201 Notes Spss, Spring 2018

Research Methods, Design, and Analysis Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner CHAPTER Twelfth Edition Quasi-Experimental Designs 10 Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Introduction • Quasi-experimental design – a research design in which an experimental procedure is applied, but all extraneous variables are not controlled – typically lacking random assignment Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Introduction • Causal inferences are made by ruling out rival hypothesis – identification and study of plausible threats to internal validity – control by design  additional pretests time points  additional control groups – coherent pattern matching  making a complex prediction that few rival hypotheses can explain Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Nonequivalent Comparison Group Design • The most common quasi-experimental design • Includes both an experimental and control group – Participants not randomly assigned to groups • Pre-test important to determine equivalence of groups – large difference between groups on pre-test may indicate selection bias • Threats frequently reveal themselves in the outcome Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Outcomes with Rival Hypotheses • Increasing treatment and control groups – greater increase in treatment condition – could be caused by a number of rival hypotheses  selection-maturation  selection-history  other selection-interactive effects Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Outcomes with Rival Hypotheses • Experimental group higher than control group at pre-test effect – no change in control group – treatment condition starts higher and increases – rival hypotheses  selection-history Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Outcomes with Rival Hypotheses • Experimental group lower than control group at pre-test effect – no change in control group – treatment condition starts lower and increases – rival hypotheses  selection-regression Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Outcomes with Rival Hypotheses • Crossover effect – treatment group scores significantly lower than the control group at pretest – significantly higher at posttest – no change in control group – rival hypotheses unlikely with this type of result Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Ruling out Threats to the Nonequivalent Comparison Group • Matching – equates the groups on important variables – example  Head Start programs can be matched on income, intelligence, and parental involvement – matching not a perfect replacement for random assignment, but can be used when random assignment is not possible – selection-regression effects may occur when using extreme groups • Statistical control techniques – ANCOVA Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Causal Inference from Nonequivalent Comparison Group Design • To increase internal validity – do not let participants self-select into groups  self-selection increases bias – minimize pretest differences in groups  matching  ANCOVA during data analysis Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Interrupted Time-Series Design • Design in which a treatment effect is assessed by comparing the pattern of pre- and posttest scores for a single group of research participants • Looking for discontinuity in the series of dependent measures • Example – Lewis and Eves (2012) Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Interrupted Time-Series Design • Use of multiple pretest and posttest measurements demonstrates reliability of effect • Visual inspection of pre and posttest measure very important to determine treatment effect • Improvement over one-group pretest-posttest design • Primary weakness – no control of history effects Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Regression Discontinuity Design • Design that assigns participants to groups based on their scores on an assignment variable and assesses the effect of a treatment by looking for a discontinuity in the groups regression lines Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Regression Discontinuity Design • Characteristics of the design – all individuals are pretested – individuals who score above some cutoff score receive the treatment – all individuals are posttested – discontinuity in the regression line indicates a treatment effect Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner Regression Discontinuity Design Copyright ©2014 by Pearson Education, Inc. All rights reserved. Research Methods, Design, and Analysis, Twelfth Edition Christensen • Johnson • Turner