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# Statistics Questions - quasi-experiments

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A. Complete Jackson Even-numbered chapter exercises, p, 360

1Describe the advantages and disadvantages of quasi-experiments? What is the fundamental weakness of a quasi-experimental design? Why is it a weakness? Does its weakness always matter?
2If you randomly assign participants to groups, can you assume the groups are equivalent at the beginning of the study? At the end? Why or why not? If you cannot assume equivalence at either end, what can you do? Please explain.
3Explain and give examples of how the particular outcomes of a study can suggest if a particular threat is likely to have been present.
4Describe each of the following types of designs, explain its logic, and why the design does or does not address the selection threats discussed in Chapter 7 of Trochim and Donnelly (2006):
Non-equivalent control group pretest only
Non-equivalent control group pretest/posttest
Cross-sectional
Regression-Discontinuity
5Why are quasi-experimental designs used more often than experimental designs?
6One conclusion you might reach (hint) after completing the readings for this assignment is that there are no bad designs, only bad design choices (and implementations). State a research question for which a single-group post-test only design can yield relatively unambiguous findings.

Part II - Answer the following questions:
1What research question(s) does the study address?
2What is Goldberg's rationale for the study? Was the study designed to contribute to theory? Do the results of the study contribute to theory? For both questions: If so, how? If not, why not?
3What constructs does the study address? How are they operationalized?
4What are the independent and dependent variables in the study?
5Name the type of design the researchers used.
6What internal and external validity threats did the researchers address in their design? How did they address them? Are there threats they did not address? If so how does the failure to address the threats affect the researchers' interpretations of their findings? Are Goldberg's conclusions convincing? Why or why not?
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Complete Jackson Even-numbered chapter exercises, p, 360

// For the purpose of exploring the role of different types of experiments and their design, there is a need of having thorough understanding of various research approaches. In this context, the presented section of the paper has explored the orientation of quasi and other types of research designs//

Exercise 1:
A true experimental design is that in which a complete control of external variables is there. Along with this, it also comprises of three essential characteristics that are manipulation, randomization, and control. In a quasi-experimental design, there is no control on the extraneous variables as it lacks manipulation and consists of randomization or control. Another difference is that true experimental design is a conscious effort of a researcher while the quasi experimental design is used to determine the causality, where random assignments are not possible. The quasi-experimental designs are more used in the real world settings while true experimental designs are used in controlled environments (Burns, 2007).

Exercise 2:
The psychology professor is interested in implementing weekly quizzes to improve students' learning. There should be use of Nonequivalent group, pretest-posttest type of quasi-experimental design. Psychology professor teaches one section only once for her introductory psychology class and not any other sections, which requires this type of quasi-experiment design as it enables to compare the pre and post test scenarios (Jackson, 2014).

Exercise 3:
Psychology professor teaches only one section of introductory psychology section and not other sections. It needs the application of pretest-posttest design type of single group designs as it provides the facility of comparison between pretest and posttest scenarios of the involved group to find the reasons for change that are due to teaching of particular subject material. It is able to highlight the clear effects and causes of the teaching that is one of the main objectives of the quasi-experiment design (Bonate, 2000).

Exercise 4:
In the second exercise, there pretest-posttest type of quasi-experimental is selected. The primary confounds for this is that it provides the facility of measuring differences between the two groups and the reasons for changes in the two groups, where one is involved in weekly quizzes and the other group is not.
In the third exercise, pretest-posttest design type of single group has been selected. The prime confound for this selection is that this research design elaborates the cause and effect relationship between two variables.

Exercise 5
Similarities in Cross-sectional, Longitudinal and Sequential Designs
• All the three designs are based on the observation in which the results are recorded without manipulating the environment.
• All the designs are primarily used to observe the changes in any study group (Tamara, 2014).
Differences between the three designs are:

Cross-sectional designs do not provide the cause and effect relationship while longitudinal and sequential designs provide the cause and effect relationship.
Cross-sectional designs are used to study different groups immediately, while longitudinal designs are used to study a single group for longer time and sequential designs are combination of both cross-sectional and longitudinal designs in which bunch of different groups are studied for a longer period of time.
Sequential designs are more beneficial in reducing the cumulative testing effects than the cross sectional and longitudinal because the tests are conducted in the chronological pattern (Tamara, 2014).

Exercise 6:
Single Case Design (SCD) is a method of evaluation, which is used in order to test the effectiveness of an intervention in a certain case. It also provides evidence related to the intervention with the help of relatively small sample size. There are various advantages of this kind of method of evaluation, which acts as a driving factor for the researchers to choose such kind of method (Franklin, Allison & Gorman, 2014).

One of the most important advantages of single case design is that it is very affordable means of research. It involves relatively low cost that makes it a very good source of group research in the early stage, which generates pilot data.
Single case design is a method that is very effective when a researcher wants to study the process of change. Therefore, the researcher can easily detect the dynamic aspects of change with the help of using single case design.
This method of evaluation also helps in fulfilling the researcher's objective of the experimental evaluation of the efficiency of a treatment for an individual.

Exercise 7:
Reversal design helps the researchers to measure the behavior of the research participants during and after the treatment. There are various advantages and disadvantages associated with the reversal design (Powell, Honey & Symbaluk, 2012). Its advantages include:
The reversal design is an effective means of evaluating the effectiveness of more than one treatment.
It is the study with the help of more than one subject, and four or more persons, which makes the results very accurate and authentic.