Analysis and Evaluation of Quasi-Experimental Designs in Educational Research

Solved assignment evaluating quasi-experimental designs in educational research.

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Quasi-experimental Design
Jackson (2012) Chapter Exercises
#2. The psychology professor has two sections of students that were not randomly
assigned. The treatment will be weekly quizzes. The desired outcome is improved student
learning. I will assume that student learning is measured by the total score on all exams not
including the weekly quizzes. This design can be diagrammed with the following notation:
N X O
N O
Based on these assumptions I would recommend a nonequivalent control group posttest only
design 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 an
alternative possibility for this design:
N X O X O
N O O
Based on these assumptions, I would recommend a nonequivalent control group time-series
design for this experiment. Overall, this later design is a stronger design because of the multiple
observations and points of comparison between the two sections.
#4. Usually the nonequivalent control group design uses intact groups. Since these
groups are not randomly selected, the major confound for this design is selection bias. Selection
bias arises when the control and experimental groups are not comparable before the study and
gives an alternative explanation for any differences in the posttest. In this design there are a
couple of social interaction threats that are possible. Students in the experimental section may
Quantitative Research 2
find out that students in the control section are not getting quizzes and react negatively, causing
resentful demoralization, or react competitively, causing compensatory rivalry. Either case
would tend “to equalize the outcomes between groups, minimizing the chance of seeing a
program 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, if
student scores are high or low, it is impossible to tell if they are that way because of the
treatment, or because of some alternative explanation. With only a single group to measure, all
of the single group threats to internal validity are possible. In this particular study the most
likely would be a history threat, where an event or set of events could affect the outcome more
than the treatment.
#6. Three reasons a researcher might choose a single-case design include, (a) when a
single 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 often
are interested in the effect of a treatment on a single individual. One study was interested in
mitigating or eliminating auditory hallucinations and delusions as a result of schizophrenia, and
evaluated the use of “an innovative rational-emotive cognitive treatment” (Qumtin, Belanger, &
Lamontagne, 2012, p. 114). From this treatment there was a noticeable and immediate reduction
in depression and anxiety and an increase in the patient’s quality of life that extended through the
12-month follow up. A discussion regarding replication of empirical results resulting from
single-case designs in psychology and education was written by Kratochwill and Levin (2010)
along with suggestions for improving the credibility of these designs by using randomization.
Error variance results from differences between participants in a group. In a single-case design
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