Exam 11: More on Experiments: Confounding and Obscuring Variables

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:

Regression is especially problematic in which of the following situations?

Dr. Sanderson is curious as to whether exposing people to violent video games causes them to be more aggressive. She assigns half her participants to play a violent video game for 5 minutes and the other half to play the same game for 25 minutes. Afterward, she has them play a board game and has a well-trained coder determine whether they are very aggressive in their playing style, barely aggressive, or not at all aggressive. She finds that a vast majority of her participants, regardless of group assignment, are rated as very aggressive. This outcome would be known as a(n):

To avoid insensitive measures, it is important to use measures that include:

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?

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?

Observer bias can threaten which of the following big validities?

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 proposes that he replicate the study and double the number of participants he recruits. State which cause(s) of within-group variability will be helped by adding more participants and why this will help.

Dr. Merrick designs a study comparing the effects of mindfulness training to cognitive training on flexible thinking. In designing this study, what would be an appropriate manipulation check?

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

Using the same setting and consistent protocols for each participant in a study will reduce the effect of:

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

Ceiling effects can lead to:

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?

Which of the following can help prevent testing effects?

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

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?

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. Provide three reasons why Armand's study may have resulted in null effects.

Dr. Gong conducts a study where she randomly assigns participants to different experimental conditions. The testing for each condition occurs in a different room of the psychology building. After collecting her data, she learns that the air conditioning in one of the rooms had been turned off during data collection. Which of the following threats to internal validity should Dr. Gong be concerned with?