Exam 8: Internal and External Validity

Andy conducts a study to improve reading scores in elementary schools. He obtains a sample of second-graders whose reading level was very much below average. He enrolls these students in a reading program and then measures their reading level six months later. Reading levels were significantly higher after the program than before. Because Andy selected participants on the basis of their extreme scores, he should be concerned about

Tracy hopes that the results of her experiment are applicable to college students in general, not just the 100 students in her study. Tracy is concerned about

Describe the internal validity threat of instrumentation and give an example.

Bonnie conducts an experiment to examine the effects of media on college women's body image. She gives a sample of women a body image questionnaire, then a week later exposes them to magazine photos of very thin models. Then a week later she administers a posttest designed to assess any changes in body image. Right before the posttest, a famous supermodel is reported to be suffering from anorexia; the story is on the cover of several magazines. Bonnie is concerned that the women's responses on the posttest may be influenced by the supermodel story instead of her independent variable. This example illustrates the potential problem of

Which of the following threats to external validity is the most difficult to deal with as a researcher?

A coder in an experiment has to code participant responses over a period of several months. The coding that she does during the first month is noticeably different from the coding she does during the last month. The experiment has ___________ problems.

A researcher does a study on a new therapy to treat anxiety. All of her participants are men; it turns out the therapy is not effective with women. This example illustrates which of the following threats to external validity?

Describe a few ways in which researchers measure aggression in the real world.

Which of the following is used by psychologists to create nonreactive measures?

In general, which has higher external validity: field research or laboratory research? Why?

What is one benefit of conducting a replication with extension instead of a replication?

Threats to internal validity that can occur if there are systematic differences between selected treatment groups based on maturation, history, or instrumentation are referred to as interactions with __________.

Describe reactive and nonreactive measures. How do reactive measures relate to internal validity?

Joy scored a 98% on her last Research Methods exam. Based on the concept of statistical regression, we would predict that her score on the next exam will be

Describe interaction of selection and treatment and give an example. Why is this a threat to external validity?

When a pretest sensitizes participants to the treatment yet to come, researchers have a problem of

Describe multiple-treatment interference and give an example. Why is this a threat to external validity?

Jerry is concerned about whether his independent variable is the only possible explanation for the results of his experiment. Jerry is concerned about

Instrumentation can refer to problems with

Ben conducts a study to test the effectiveness of an alcohol treatment program. He surveys the clients twice: once at intake and again six months later. He finds that overall, the treatment program was effective, but approximately 30% of the original sample dropped out of the program so he does not have posttest data for them. Ben has encountered which kind of problem?