Exam 10: 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?

Unsystematic variability in a study is also known as:

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?

RESEARCH STUDY 10.3 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 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. -Refer to Research Study 10.3 above to answer the following question. 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).What kind of threat to internal validity does this pose? How does this affect her conclusion that her treatment for homesickness worked?

All of the following are true of ceiling and floor effects EXCEPT:

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

Which of the following threats to internal validity can occur in any study?

Which of the following study types can result in a null effect?

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

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

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

RESEARCH STUDY 10.2 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). -Refer to Research Study 10.2 above to answer the following question. 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?

RESEARCH STUDY 10.4 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. -Refer to Research Study 10.4 above to answer the following question. 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.

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

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

RESEARCH STUDY 10.3 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 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. -Refer to Research Study 10.3 above to answer the following question. 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?

RESEARCH STUDY 10.2 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). -Refer to Research Study 10.2 above to answer the following question. Which of the following threats to internal validity will Dr.Bloedorn NOT be worried about?

RESEARCH STUDY 10.2 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). -Refer to Research Study 10.2 above to answer the following question. Imagine that Dr.Bloedorn finds no difference between the calories consumed with the drink additive and without.This is known as:

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

Observer bias can threaten which of the following big validities?