Exam 13: Quasi-Experiments and Small-N Designs

How does a researcher who conducts a small-N design address external validity concerns about his study?

Researchers may be interested in how a variable changes over the course of a major event that is scheduled outside of experimental control. This is called:

Dr. Fletcher is interested in understanding whether joining a fraternity/sorority causes people to become more concerned about their attractiveness and appearance. He recruits a group of 55 freshmen (25 males, 30 females) who are planning to go through fraternity/sorority recruitment on his campus. After they join, he gives them a measure of attractiveness concern/appearance concern (the Body Concern Scale, where higher scores indicate higher body concerns). In addition to measuring the group of participants who joined a fraternity/sorority, Dr. Fletcher decides to give the same measure to another group of 55 participants who decided to not join a fraternity/sorority. Based on the results below, explain whether Dr. Fletcher should be concerned about a history threat to internal validity.

Which of the following is a difference between true experiments and quasi-experiments?

Dr. LaGuardia is a cognitive neuroscientist who is interested in the effect of brain concussions on the ability to recognize faces. He conducts a quasi-experimental study in which he examines football players before and after the regular season using the Benton Facial Recognition Test (a published, widely used measure of one's ability to recognize faces) to compare those who received concussions to those who did not. He finds that players who had concussions during the regular season performed worse on the Benton Facial Recognition Test than did players who did not experience concussions. In interrogating the construct validity of Dr. LaGuardia's study, which of the following statements is accurate?

In a nonequivalent control group interrupted time series design, the independent variable is studied as:

Provide a reason a researcher might want to conduct a small-N design. Provide a reason why a researcher might want to avoid conducting a small-N design.

Dr. Anderson is a nutritionist who helps clients lose weight prior to surgery. She is working with W. J., a male client who is planning on undergoing a heart transplant. He currently eats more than 3,500 calories a day and has been asked by his doctor to cut the number of calories to about 1,800 (400 for breakfast, 600 for lunch, and 800 for dinner). She is curious as to whether a food journal will help W. J. reduce the number of calories he eats. A food journal is used to record everything a person eats to help patients be more aware of what they're eating. W. J.'s wife also recorded the food he consumed at each meal to have complete data before introducing the journal. Dr. Anderson decides to phase in the food journal gradually, initially only having W. J. record what he ate at breakfast during the first three days after baseline (days 4-6). During days 7-9, the journal is used at lunch, too, and during days 10-12, it also is used during dinner. The data for Dr. Anderson's study are below. In examining the external validity of her study, Dr. Anderson is probably most concerned about making sure her study generalizes to:

Explain why quasi-experiments offer a trade-off between internal validity and external validity.

Dr. Fletcher is interested in whether joining a fraternity/sorority causes people to become more concerned about their attractiveness and appearance. He recruits a group of 55 freshmen (25 males, 30 females) who are planning to go through fraternity/sorority recruitment on his campus. After they join, he gives them a measure of attractiveness concern/appearance concern (the Body Concern Scale). If Dr. Fletcher is interested in a causal relationship between joining a fraternity/sorority and attractiveness/appearance concern, why doesn't he conduct a true experiment?

Dr. Fletcher is interested in understanding whether joining a fraternity/sorority causes people to become more concerned about their attractiveness and appearance. He recruits a group of 55 freshmen (25 males, 30 females) who are planning to go through fraternity/sorority recruitment on his campus. After they join, he gives them a measure of attractiveness concern/appearance concern (the Body Concern Scale, where higher scores indicate higher body concerns). As the study is described, explain a selection threat that may be present in Dr. Fletcher's study. What could Dr. Fletcher do to address this threat?

Dr. Fletcher is interested in understanding whether joining a fraternity/sorority causes people to become more concerned about their attractiveness and appearance. He recruits a group of 55 freshmen (25 males, 30 females) who are planning to go through fraternity/sorority recruitment on his campus. After they join, he gives them a measure of attractiveness concern/appearance concern (the Body Concern Scale, where higher scores indicate higher body concerns). Explain why Dr. Fletcher is conducting a quasi-experimental design rather than a true experiment.

Which of the following is an advantage of small-N designs over large-N designs?

Explain how interrogating the statistical validity of a small-N design is different from interrogating the statistical validity in a large-N design.

Why do quasi-experiments tend to have very good construct validity for the independent variable?

Dr. Anderson is a nutritionist who helps clients lose weight prior to surgery. She is working with W. J., a male client who is planning on undergoing a heart transplant. He currently eats more than 3,500 calories a day and has been asked by his doctor to cut the number of calories to about 1,800 (400 for breakfast, 600 for lunch, and 800 for dinner). She is curious as to whether a food journal will help W. J. reduce the number of calories he eats. A food journal is used to record everything a person eats to help patients be more aware of what they're eating. W. J.'s wife also recorded the food he consumed at each meal to have complete data before introducing the journal. Dr. Anderson decides to phase in the food journal gradually, initially only having W. J. record what he ate at breakfast during the first three days after baseline (days 4-6). During days 7-9, the journal is used at lunch, too, and during days 10-12, it also is used during dinner. The data for Dr. Anderson's study are below. Which of the following is evidence that would allow Dr. Anderson to conclude that keeping a food journal caused weight loss in W. J.?

Dr. Fletcher is interested in whether joining a fraternity/sorority causes people to become more concerned about their attractiveness and appearance. He recruits a group of 55 freshmen (25 males, 30 females) who are planning to go through fraternity/sorority recruitment on his campus. After they join, he gives them a measure of attractiveness concern/appearance concern (the Body Concern Scale). In addition to measuring the group of participants who joined a fraternity/sorority, Dr. Fletcher decides to give the same measure to another group of 55 participants who decided to not join a fraternity/sorority. After conducting the study, Dr. Fletcher finds out that the people who joined a fraternity/sorority all saw a documentary on body image sponsored by the InterGreek Council the night before recruitment began. This threat to internal validity is known as a:

Dr. LaGuardia is a cognitive neuroscientist who is interested in the effect of brain concussions on the ability to recognize faces. He conducts a quasi-experimental study in which he examines football players before and after the regular season using the Benton Facial Recognition Test (a published, widely used measure of one's ability to recognize faces) to compare those who received concussions to those who did not. He finds that players who had concussions during the regular season performed worse on the Benton Facial Recognition Test than did players who did not experience concussions. Which of the following makes Dr. LaGuardia's quasi-experimental study different from a correlational study?

Dr. LaGuardia is a cognitive neuroscientist who is interested in the effect of brain concussions on the ability to recognize faces. He conducts a quasi-experimental study in which he examines football players before and after the regular season using the Benton Facial Recognition Test (a published, widely used measure of one's ability to recognize faces) to compare those who received concussions to those who did not. He finds that players who had concussions during the regular season performed worse on the Benton Facial Recognition Test than did players who did not experience concussions. Which of the following is true regarding external validity in Dr. LaGuardia's study?

In which of the following ways are correlational designs similar to quasi-experimental designs?