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Identifying Confounding Variables

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Identify any confounding variable(s) in the following studies and comment about whether the sample is representative of the population of interest. Look for confounding variables that are obviously present in the study.

A. You are studying the effects of "pep talks" on performance. You randomly select 50 undergraduates from the college's enrollment records; all 50 agree to participate. The first 25 students who come through the door are sent to the gym, where they are given a brief pep talk. The next 25 students who come through the door are sent to the concert hall, where they receive a dry lecture (a "fake" treatment). You record the number of errors on a simple task and compare the number of errors between groups. (So, the IV is the type of talk presented and the DV is the number of errors on a task.) You find that the pep talk group makes fewer errors.

D. You want to know whether child abuse is increasing in the US, particularly among upper middle class individuals. You call all pediatricians in your home city (all 25 of them). 10 return your calls; you ask them whether child abuse rates have increased over the past 10 years.

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Confounding variables

If a treatment is manipulating more than a variable it is stated to be a confounding variable. In a more formal definition, Mitchell and Jolley (2005) define confounding variables as "variables that are manipulated along with the treatment" (p.300). Confounding variables make it known whether the treatment had an effect. In any experiment there may be variables that confound the results (because of an error). These variables may not have not been measured and may vary within ...

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This solution explores the identification of confounding variables in specific studies/

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Articulate extraneous variables, confounding variables, and representative samples.

Let's work on extraneous variables, confounding variables, and representative samples. Identify any confounding variable(s) in the following studies and comment about whether the sample is representative of the population of interest. Look for confounding variables that are obviously present in the study. . . . avoid speculating about items that are not mentioned.

A. You are studying the effects of wording of a survey question on response to the survey. You randomly assign 50 people to group A and 50 people to group B. You read a survey to group A; all of the questions include the word "not". Your assistant reads a survey to group B; all of the questions are the same but have been reworded to eliminate the word "not" (note that the meaning of the questions is exactly the same in both groups; just the wording is different). You compare the response to the survey between the two groups. The IV is wording of the survey questions and the DV is the score on the survey.

B. You want to know whether most people process information more easily when it is presented orally vs when it is presented in written form. The participants are students in a marching band course. You administer the same quiz twice to each participant; first the quiz administered orally; a week later the same quiz is administered in written form. You find that most people make fewer mistakes when the quiz was presented in written form. (The IV is the format of the quiz; the DV is score on the quiz.)

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