Exam 11: More on Experiments: Confounding and Obscuring Variables

Dr.Morimoto is curious as to whether exposing people to violent video games causes them to be more aggressive.He assigns half his participants to play a video game for five minutes and the other half to play for seven minutes.He finds that there is no relationship between playing the game longer and being more aggressive.What might be to blame for this null effect?

Which of the following things CANNOT be done to reduce the effect of individual differences?

In previous studies,Dr.Schulenberg has established that finding meaning in one's everyday work activities can lead to greater success in the workplace (e.g. ,productivity,creativity).He is curious as to whether this can happen in the college classroom.Specifically,he is curious whether finding meaning in one's classroom experience can lead to greater academic performance.In the spring semester,he has his teaching assistant randomly assign half the class to write a paragraph each class period about how the material has meaning for their lives (meaning group).The other half writes a paragraph about what they did to prepare for class (preparation group).He does not know which of his students are writing which paragraph,and the students are not aware they are responding to different writing assignments.To measure academic performance,he gives the students a midterm essay exam and a final exam. -Imagine that in Dr.Schulenberg's study,he notes that all of the students do extremely well on the midterm exam.When he looks at the results of the final exam,he notices that all the students' exam scores went down.Given this information,which of the following threats might be present in his study?

Dr.Paddock is a counseling psychologist who is interested in decreasing adjustment issues in first-year college students.She is curious if having students create collages of their first few weeks of school and then mailing them home will help students feel they have integrated their new life with their old and,as a result,will help them feel less homesick.She samples a group of 100 incoming college freshmen at her university and measures how homesick they are during the first week of school.During Week 4 of school,she has them make the collage and send it home.During Week 7 of school,she measures their homesickness again.She notices a significant reduction in the amount of homesickness from the pretest to the posttest and concludes that her treatment is effective. -Imagine in Dr.Paddock's study that only 90 of the original participants completed the measure of homesickness during Week 7 (10 participants had left the university and were unavailable).Name two things that Dr.Paddock can do to address this possible threat to internal validity and why these should be done.

A participant's score on a dependent variable is a combination of which of the following:

Explain why null effects are important in science but are hard to find in the popular press.

Dr.Paddock is a counseling psychologist who is interested in decreasing adjustment issues in first-year college students.She is curious if having students create collages of their first few weeks of school and then mailing them home will help students feel they have integrated their new life with their old and,as a result,will help them feel less homesick.She samples a group of 100 incoming college freshmen at her university and measures how homesick they are during the first week of school.During Week 4 of school,she has them make the collage and send it home.During Week 7 of school,she measures their homesickness again.She notices a significant reduction in the amount of homesickness from the pretest to the posttest and concludes that her treatment is effective. -Name two threats to internal validity that are likely to be present in Dr.Paddock's study,given her particular design.What other explanation do these threats provide for the results found by Dr.Paddock?

Dr.Paddock is a counseling psychologist who is interested in decreasing adjustment issues in first-year college students.She is curious if having students create collages of their first few weeks of school and then mailing them home will help students feel they have integrated their new life with their old and,as a result,will help them feel less homesick.She samples a group of 100 incoming college freshmen at her university and measures how homesick they are during the first week of school.During Week 4 of school,she has them make the collage and send it home.During Week 7 of school,she measures their homesickness again.She notices a significant reduction in the amount of homesickness from the pretest to the posttest and concludes that her treatment is effective. -Imagine in Dr.Paddock's study that the pretest scores were incredibly high,indicating a large amount of homesickness in her sample.What kind of threat to internal validity does this pose? How does this affect her conclusion that her treatment for homesickness worked?

A confound that keeps a researcher from finding a relationship between two variables is known as a/an:

Which of the following things CANNOT be done to reduce measurement error?

The addition of a comparison group can address all of the following threats to internal validity EXCEPT:

What is a double-blind study? Explain how this design addresses both the issue of demand characteristics and the issue of observer bias.

Which of the following studies would NOT have a possible threat of observer bias?

Observer bias can threaten which of the following big validities?

Spontaneous remission in clinical studies is an example of which of the following threats to internal validity?

Which of the following is true of instrumentation threats?

Armand conducts a study for his research method class.He is curious as to whether watching romantic movies makes people more committed to their romantic relationship.He collects a sample of men in dating relationships and divides them into two groups.One group watches a 5-minute clip of a movie in which the main characters are having a romantic first date.The second group watches a 5-minute clip from the same movie in which the main characters break up.After the participants watch the movie clip,they are then asked to write a sentence about their relationship.Armand counts the number of uses of the words we and us as a measure of commitment.After conducting the study,he finds that there is not a statistically significant difference between his two groups. -Armand's professor suggests that the null effect may be due to a large amount of within-group variance.State three causes of within-group variance in Armand's study.

Explain how within-group variance can obscure between-group differences.

Which of the following is NOT true of testing effects?

Name two study designs that would address issues of individual differences contributing to within-group variance.If these two designs are not possible,what else could a researcher do?