Exam 11: More on Experiments: Confounding and Obscuring Variables

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. -What is a comparison group? What kind of comparison group could Dr.Paddock add to her study to address several threats to internal validity? (In other words,what would this comparison group do/not do?)Explain why this addition would help address threats to internal validity.

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?

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.

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?

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. -The study described above is an example of which of the following?

A decrease in participants' scores on a measure from pretest to posttest could suggest all of the following threats to internal validity EXCEPT?

Testing threats involve ________ whereas instrumentation threats involve ________.

Why is there a publication bias against null effects?

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?

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?

A researcher's attempt to control sounds,smells,and even temperature in a testing environment is meant to reduce which of the following?

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 NOT recommend to her as a way to address this type of threat?

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

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?

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.

Which of the following threats to internal validity CANNOT occur in just any study?

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

Dr.LaGuardia is curious as to whether children in a daycare center will share more after watching an educational video on sharing.Immediately before and after the video,he has several undergraduate research assistants code the sharing behavior of a group of 33 four-year-olds.Which of the following would you NOT recommend to him to decrease the threat of instrumentation?

Which of the following is NOT a reason a researcher might choose to conduct a double-blind placebo control group study?

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