Application: Generalization and External Validity

In the Discussion for this week, you addressed one of the internal threats to validity, that is, confounding variables. This Assignment will challenge you on external threats to validity.

In this week’s Discussion scenario, the Instructor examined the effectiveness of a reading comprehension strategy across two groups of students. Imagine the Instructor had administered a pretest to compare the two groups’ reading comprehension scores, prior to the delivery of the new reading comprehension strategy, and had found no significant difference between the groups. In that case, the Instructor might have been able to assert that the intervention was responsible for the observed change. This would have eliminated the possible confound that students enrolled in the second term, on average, had better reading comprehension skills at the start of the study. Therefore, the new reading comprehension strategy might have actually helped the students who applied it to improve their reading comprehension efficiency.

Suppose another study from a corporate publication reported that the same reading comprehension strategy was shown to be ineffective when tested among a population of business analysts. It did not help improve their reading comprehension of corporate research publications. Therefore, the reading comprehension strategy used with psychology students did not generalize across populations or settings.

For this week’s Assignment you examine the concept of generalization and apply various types of replications to examples of psychological studies, both of which relate to external validity.

To prepare:

  • Review the assigned pages in Chapter 13 of the course text.
  • You may also review and research materials (hard copies or online) outside this week’s Learning Resources that are relevant to the Assignment, if you wish.

The Assignment (1–2 pages):

  • Explain the two main types of generalizations and identify the issues associated with each type.
  • Explain the four different types of replications and the purpose of each. Include for each type of replication an original psychological study example (i.e., make up your own) that is different for each type of replication (i.e., do not build on the same example). Plan to devote a short paragraph for each.
  • Briefly explain how replications relate to external validity.

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