Exam 11: More on Experiments: Confounding and Obscuring Variables

Which of the following is NOT a reason that a study might yield a null result?

Dr. Deveraux has conducted a study that has resulted in a null effect. Nonetheless, she suspects that there truly is a causal relationship between her independent and dependent variables. Which of the following is UNLIKELY to be to blame?

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

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.

When interrogating experiments, on which of the big validities should a person focus?

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

Ceiling effects can affect:

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

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. Which of the following pattern of results would suggest that there is a threat to internal validity?

Which of the following cannot be found in a one-group, pretest/posttest design?

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

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 group that does not use the drink additive but adds a similar-looking substance that they think is the additive would help Dr. Bloedorn address which of the following threats to internal validity?

Which of the following threats to internal validity can apply even when a control group is used?

Which of the following things can be done to reduce measurement error?

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

The addition of a comparison group can address which of the following threats to internal validity?

What can researchers do to reduce the risk of measurement error?

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 5 minutes and the other half to play for 7 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?

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?

Which of the following is a reason why a researcher might choose to conduct a double-blind placebo control group study?