Chapter 2

Very brief chapter overview

This chapter shows you some of the pitfalls of blindly applying methods from other sciences to psychology (pay close attention the problems of internal, external, and construct validity, as well as ethical issues--you'll see these concepts again!).

Chapter Summary

 At one level, there are two basic problems about doing research to get answers to questions about human behavior.

  1. The study you do may be unethical.
  2. The study you do may not answer the question.
At another level, there is only one problem: Is the study ethical?
According to APA"s ethical principles (which every researcher should consult before doing a study), a study is ethical if the potential benefits of the study outweigh the study's potential for harm. Thus, there are two ways to increase the chances that your study is ethical.
First, reduce the potential for harm. Following the nine guidelines in Table 2-2 (p. 36) can help reduce the potential for harm.
Second, make your study worth doing. This means
  1. Having an interesting, important research question; and
  2. Collecting data that will allow you to answer that question.
Mitchell and Jolley address point 1 (developing an interesting, important research question) in Chapter 3. But what about point 2 (collecting data that will allow you to answer your research question)? Obviously, your study should have validity. But what type of validity? The type of validity you will need will depend on your research question.

If your research question is about whether something causes a certain effect, your study must have internal validity. As you'll see later, only experimental designs have internal validity, which allows you to make cause-effect statements. Thus, if you want to make cause-effect statements, you should do an experiment.
Alternatively, if your research question is about what percentage of people do some behavior, you need a study that has external validity. One key to having external validity is to have a large, random, representative sample of participants. This helps you to generalize your results to a larger population.
If your research question involves measuring or manipulating some state of mind (hunger, stress, fear, motivation, love, etc.), then you need construct validity. As you'll see in Chapter 5, achieving construct validity is not easy.
Depending on the research question, you may often be interested in only one of these kinds of validity. Sometimes, you may want to have two of these kinds of validity. Rarely, however, will a study have all three types of validity.

Tip: Understanding the differences among the three types of validity takes some students a long time. To be one of the students who learns these key distinctions quickly, study Table 2-1 (p. 27). Then, test your understanding by doing some of the end-of-chapter exercises.

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