Exam 11: More on Experiments: Confounding and Obscuring Variables

Name the three threats to internal validity that can occur in studies regardless of the use of a comparison group.Why doesn't a comparison group help in these cases?

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

RESEARCH STUDY 11.2: Dr.Bloedorn is a health psychologist who researches nutrition.She is curious as to whether a new drink additive will help people consume fewer calories during a meal.The drink additive is a white, odorless, tasteless powder that a person can add to any drink.She collects a random sample of 63 overweight students on campus and measures the calories they eat during lunch using a bomb calorimeter.She then gives this additive to the same 63 participants to use at dinner and measures how many calories they eat (again using the bomb calorimeter). Imagine that Dr.Bloedorn finds no difference between the calories consumed with the drink additive and without.This is known as:

Dr.Hoff is curious as to whether children in a kindergarten classroom will be friendlier after talking about friendship.Immediately before and after the discussion, she has several undergraduate research assistants code the "friendliness" of a group of kindergarteners.Which of the following threats should Dr.Hoff be most concerned about?

RESEARCH STUDY 11.3: 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 mail 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?

After finding a null result in her study, a researcher decides to conduct a follow-up study where she limits who the findings will generalize to.Which cause of within-group variance is she trying to reduce?

RESEARCH STUDY 11.1: 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. Dr.Schulenberg likely designed his study so that neither he nor his students knew which group they were in to address which of the following?

RESEARCH STUDY 11.4: 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.

Which of the following is true of ceiling and floor effects?

Explain what a manipulation check is and how it can be used to address issues of weak manipulations and insensitive measures.

Why is there a publication bias against null 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?

RESEARCH STUDY 11.2: Dr.Bloedorn is a health psychologist who researches nutrition.She is curious as to whether a new drink additive will help people consume fewer calories during a meal.The drink additive is a white, odorless, tasteless powder that a person can add to any drink.She collects a random sample of 63 overweight students on campus and measures the calories they eat during lunch using a bomb calorimeter.She then gives this additive to the same 63 participants to use at dinner and measures how many calories they eat (again using the bomb calorimeter). The addition of a control group that does not use the drink additive would help Dr.Bloedorn address which of the following threats to internal validity?

Dr.Anderson conducted a study investigating whether exercising immediately before an exam boosted cognitive abilities.She randomly assigned participants to either do jumping jacks or count to 60 before giving them a geometry test.She did not find any differences between groups but believes there may have been a ceiling effect.What might be a clue that this was the case?

RESEARCH STUDY 11.1: 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?

Which of the following threats to internal validity would result in group differences prior to the start of the study?

Dr.Whetstone is curious about how self-esteem changes as a result of a new counseling program.She is concerned about testing threats in her study.Which of the following would you recommend to her as a way to address this type of threat?

Unsystematic variability in a study is also known as:

Which of the following is NOT a method researchers used to identify or correct for attrition?

Which of the following is true of instrumentation threats?