Analysis and Evaluation of Quasi-Experimental Designs in Educational Research

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1Quasi-experimental DesignJackson (2012) Chapter Exercises#2.The psychology professor has two sections of students that were not randomlyassigned. The treatment will be weekly quizzes. The desired outcome is improved studentlearning. I will assume that student learning is measured by the total score on all exams notincluding the weekly quizzes. This design can be diagrammed with the following notation:NXONOBased on these assumptions I would recommend a nonequivalent control group posttest onlydesign for this quasi experiment.If student learning is measured by scores on major exams through the course, however,the notation changes, as would the recommendation. The following notation represents analternative possibility for this design:NXOXONOOBased on these assumptions, I would recommend a nonequivalent control group time-seriesdesign for this experiment. Overall, this later design is a stronger design because of the multipleobservations and points of comparison between the two sections.#4.Usually the nonequivalent control group design uses intact groups. Since thesegroups are not randomly selected, the major confound for this design is selection bias. Selectionbias arises when the control and experimental groups are not comparable before the study andgives an alternative explanation for any differences in the posttest. In this design there are acouple of social interaction threats that are possible. Students in the experimental section may

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Quantitative Research2find out that students in the control section are not getting quizzes and react negatively, causingresentful demoralization, or react competitively, causing compensatory rivalry. Either casewould tend “to equalize the outcomes between groups, minimizing the chance of seeing aprogram effect even if there is one” (Trochim & Donnelly, 2008, p. 171).A single-group design’s worst confound is that there is no comparison group, therefore, ifstudent scores are high or low, it is impossible to tell if they are that way because of thetreatment, or because of some alternative explanation. With only a single group to measure, allof the single group threats to internal validity are possible. In this particular study the mostlikely would be a history threat, where an event or set of events could affect the outcome morethan the treatment.#6.Three reasons a researcher might choose a single-case design include, (a) when asingle person or condition is of interest, (b) when replication of results is essential, and (c)situations in which error variance needs to be eliminated (Jackson, 2012). Clinical trials oftenare interested in the effect of a treatment on a single individual. One study was interested inmitigating or eliminating auditory hallucinations and delusions as a result of schizophrenia, andevaluated the use of “an innovativerational-emotive cognitive treatment” (Qumtin, Belanger, &Lamontagne, 2012, p. 114). From this treatment there was a noticeable and immediate reductionin depression and anxiety and an increase in the patient’s quality of life that extended through the12-month follow up. A discussion regarding replication of empirical results resulting fromsingle-case designs in psychology and education was written by Kratochwill and Levin (2010)along with suggestions for improving the credibility of these designs byusing randomization.Error variance results from differences between participants in a group. In a single-case design

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Quantitative Research3there is no group, hence no error variance; making the determination of outcomes resulting fromthe independent variable much less complicated.#8.Single case designs can be implemented in a number of ways. In a reversal designthe focus is on a single participant, a single behavior, or a single situation, and involves theindependent variable being applied and removed one or more times to assess its impact. Byevaluating the behavior without the treatment applied and then comparing the behavior aftertreatment, a determination can be made regarding the treatments effect. Succeeding periods ofnon-treatment are called the reversal and can demonstrate what happens to the behavior with areturn to the baseline. A reversal design is very similar to a within-subjects group designbecause each subject experiences both the control and experimental condition. Greenhoot (2003)summarized that the reversal of an effect because of the removal of a treatment provided “strongevidence for a causal link between the independent and dependent variable” (p. 98).In a multiple-baseline design multiple participants, behaviors, or situations may beinvolved. In these single case studies the measures of interest are individualized and descriptivestatistics are not used to aggregate them. The multiple-baseline design measures the effect of theapplication of a treatment at differing times for multiple subjects, or can be used with a singlesubject by applying the treatment in conjunction with different behaviors or in differentscenarios.Part I Assignment Question AnswersDescribe the advantages and disadvantages of quasi-experiments? What is thefundamental weakness of a quasi-experimental design? Why is it a weakness? Does itsweakness always matter?A quasi-experimental design has certain advantages, including; (a)the ability to “draw slightly stronger conclusions than . . . with correlational research” (Jackson,

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Quantitative Research42012, p. 342), (b) contributing original research to the body of knowledge in a field (Ellis &Leavy, 2011), (c) allowing real-world research in the field as opposed to more controlledconditions (Jackson, 2012), (d) may involve an independent variable that is nonmanipulated(Hoadley, 2004), and (e) can be used with intact groups (de Anda, 2007). The disadvantages ofusing a quasi-experimental design are that (a) it “limits internal validity in a study” (Jackson,2012, p. 342), (b) does not establish a causal relationship between variables (Jackson, 2012),while (c) probabilistic equivalence cannot be assumed (Dimitrov & Rumrill, 2003). Thefundamental weakness of a quasi-experimental design, and what makes it “quasi”, is that it doesnot involve random assignment of participants to experimental conditions (Greenhoot, 2003).Nonrandom assignment weakens internal validity, diminishes the ability to establish cause-and-effect by eliminating the expectation that groups are equivalent. This weakness does not excludequasi-experiments from a researchers arsenal because of the advantages mentioned above. Theseadvantages make quasi-experiments the most used form of quantitative research (Ellis & Leavy,2011). There may be times when subjects cannot be randomly assigned to groups, there is onlyone subject of interest, or the topic of research either exists or it does not; in all of these cases aquasi-experiment is a viable option for conducting the research while an experiment is not(Greenhoot, 2003).If you randomly assign participants to groups, can you assume the groups areequivalent at the beginning of the study?At the end?Why or why not?If you cannotassume equivalence at either end, what can you do?Please explain.If participants arerandomly assigned to groups from the same population of interest to the study, the groups can besaid to be probabilistically equivalent at the beginning of a study (Trochim & Donnelly, 2008).Random assignment does not ensure groups are exactly the same, but that differences between

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