Question details

This week you explore internal validity. Internal validity tells you if
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Discussion week 4

PSYC-3003-2,Methods in Psyc Inquiry.

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Readings

  • Stangor, C. (2013). Research methods for the behavioral sciences (4th ed., Laureate Education custom ed.). Belmont, CA: Wadsworth Cengage Learning.
    • Chapter 12, “Experimental Control and Internal Validity”
    • Chapter 13, “External Validity” (pp. 254–263)

Optional Resources

  • Stangor, C. (2011). Research methods for the behavioral sciences (4th ed.). Belmont, CA: Wadsworth Cengage Learning. (Note: This reference is only for the PowerPoint version of the course.)
    • PowerPoint Presentation: Chapter 12
    • PowerPoint Presentation: Chapter 13

This electronic presentation to be used with Stangor. Research Methods for the Behavioral Sciences, 4E. From Stangor. Research Methods for the Behavioral Sciences, 4E. © 2011 South-Western, a part of Cengage Learning, Inc. All rights reserved. Reproduced by permission. Text/images may not be modified or reproduced in any way without prior written permission of the publisher. www.cengage.com/permissions

Confounding Variables

This week you explore internal validity. Internal validity tells you if you can really trust conclusions that appear to show that an independent variable causes an effect on a dependent variable. Was it really the independent variable or did something else contribute to the effect?

For example, presume that your Instructor for a psychology course wants to test if a new reading comprehension strategy improves reading efficiency of students. Your Instructor runs the study through two successive quarters of the same course. For the first quarter, he instructs the students to read a passage about a psychological study obtained from a peer-reviewed journal and then complete a comprehension test over the passage. The Instructor repeats the procedure during the second quarter. However, this time he teaches the students the new reading comprehension strategy prior to their reading the passage and taking the test.

Next, the Instructor compares the test scores obtained from the first and second quarters and finds that the students enrolled in the second quarter of the course scored significantly higher than students enrolled in the first quarter. Your Instructor happily infers that the new reading comprehension strategy he presented to the students during the second quarter of the course helps to improve reading comprehension efficiency.

What else could explain the difference in scores? Is it possible that there were more students enrolled in the second term of the course who entered with already high reading comprehension skills? What if one group already knew more about the information in the reading passage? Was a new passage chosen each time or was it the same one again? There could be many different confounding variables, which are other possible causes for the differences in scores. These pose a threat to the internal validity of this study.

For this week’s Discussion, you examine confounding variable(s) in a research study from your course text and apply measures for addressing this internal validity challenge.

To prepare:

  • Read Chapter 12 in your course text.
  • Read the Research Project Ideas scenarios in Chapter 12, pages 251–253.
  • Choose the scenario that most interests you. For your chosen scenario, determine the confounding variable(s) (there may be more than one), and consider how they might be eliminated.
  • Indicate the letter of the scenario you selected in the subject field of your posting. Select a letter that has not yet been chosen, if you are coming to the Discussion later. All nine (a–i) letters should first be used up before they can be repeated again.

With these thoughts in mind:

Post by Day 3 a description of the confounding variable(s) in your chosen scenario, and a justification for why you consider them to be confounds. Drawing from the Learning Resources this week, discuss a research design and/or procedure, the researcher(s) could utilize to eliminate the confounding variables.

Note: You can assume that random assignment took care of any potential differences in the groups and therefore group differences are not a potential confound.

Important: Indicate the letter of the scenario you selected in the subject field of your posting. You will be asked to respond to a colleague who selected a different scenario. Select a different letter from others if you are coming to the Discussion later. All nine (a-i) should first be used up before they are repeated again.

Note: Be sure to support your postings and responses with specific references to the Learning Resources.

Read a selection of your colleagues’ postings.

Available solutions