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    Experimental Design References

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    In a paper, answer the following questions:
    1. Jackson (2012) even-numbered Chapter Exercises (p. 244).
    - You read in a health magazine about a study in which a new therapy technique for depression was examined. A group of
    depressed individuals volunteered to participate in the study, which lasted 9 months. There were 50 subjects at the beginning
    of the study and 29 at the end of the 9 months. The researchers claimed that of those who completed the program, 85%
    improved. What possible confounds can you identify in this study?

    - What are internal validity and external validity, and why are they so important to researchers?

    - What are the similarities and differences between within-subjects and matched-subjects

    2. What is the purpose of conducting an experiment? How does an experimental design accomplish its purpose?
    3. What are the advantages and disadvantages of an experimental design in a business study?
    4. What is more important in an experimental study, designing the study in order to make strong internal validity claims or strong external validity claims? Why?
    5. In an experiment, what is a control? What is the purpose of a control group? Of single or multiple comparison groups?
    6. What are confounds? Give an example of a design that has three confounds. Describe three ways to alter the design to address these confounds and explain the advantages and disadvantages of each.
    7. What does "cause" mean and why is it an important concept in research? How are correlation and causation related?
    8. You are a researcher interested in addressing the question: does smiling cause mood to rise (i.e., become more positive)? Sketch between-participants, within-participants, and matched-participants designs that address this question and discuss the advantages and disadvantages of each to yielding data that help you answer the question. Describe and discuss each design in 4-5 sentences.

    References: At least five (5) resources. In addition to these specified resources, other appropriate scholarly resources, including older articles, may be included.

    Length: 5- 7 pages

    Use current APA standards.

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    Solution Preview

    In compliance with BrainMass rules this is not a hand in ready report but is only guidance.
    For sketches, please see the attachment.
    There were 50 subjects at the beginning of the study and only 29 at the end of 9 months. The first confound that could have affected the experiment is history confound where an event that affects the outcome variable occurs between pretreatment measurement and post treatment measurement. For example, in this case it is possible that twenty-one subjects who were part of the study at the beginning had died. The second confound is maturation confound. Maturation confound occurs if participants could have develop between pre- and posttest measurement of the outcome variable. For example, In this case 21 of the 50 depressed individuals could have experienced increased depression forcing them to leave the experiment. In such a situation the conclusions of the program are erroneous.

    Internal validity means how well an experiment is done. This means examining whether it avoids confounding. The lower the possibility of the presence of confounds, the higher is the experiment's internal validity. It is important because high internal validity means that it was the treatment that caused the change in the subject.
    External validity means the extent to which a study's results can be generalized to other people or settings. This is important because external validity determines the applicability of the results of the experiment to other situations. In general group research using randomization will possess higher external validity than will studies that do not use random selection.

    A matched subject design uses separate experimental groups for each treatment but relies on matching every subject in one group with an equivalent in another. A within subjects design uses the same group of subjects in more than one treatment. The similarities are that in both the cases treatments are given to the relevant groups. There is pre-testing and post-testing measurement. The differences are that in a within subjects design the same group of subjects is used for several treatments. In case of matched subject design a different experimental group is used for each treatment but matches every subject in one group with an equivalent in another.

    The purpose of conducting an experiment is test the hypothesis by examining the relationships between independent and dependent variables (1). The purpose of conducting an experiment is to scientifically test a hypothesis. The purpose is to understand the causal process.
    The experimental design accomplishes this purpose by having two groups of subjects, an experimental group and a control group. The ...

    Solution Summary

    The response provides you a structured explanation of experimental design. It also gives you the relevant references.