Research Method

PS276: Research Methods

Homework: Chapters 10 & 11

Due: Sunday, 5/2 by midnight

Overview: Please answer the following questions related to content covered in Chapters 10 and 11. Feel free to use your textbook and the slides to help answer these questions, but please make sure to put everything in your own words (bullets are totally acceptable!) The questions to answer are highlighted!

1. Design a posttest-only experiment that would test the causal claim below. For your study identify the independent variable(s), identify its dependent variable(s), and suggest some important control variables. Finally, apply the three causal criteria (covariance, temporal precedence and internal validity) to the study.

· Claim: Drinking sugared ice tea (compared to sugar-free ice tea) makes people better able to perform well on a self-control task.

a. Posttest-only study design (how would you test that claim using this design?):

b. Independent Variable:

c. Dependent Variable:

d. Control Variables:

e. How does your study design show covariance, temporal precedence and internal validity?

2. Below you will find 3 variations on a simple experiment (the simple experiment is described below). Each of these variations demonstrate a threat to internal validity that was discussed in Chapter 10 or 11. Your job is to identify the experiment design and the main threat to internal validity for each variation.

Simple Experiment Set-up:

· Research Question : TV ads promote online “brain games” and learning tools for adults and kids. A researcher decided to test the effectiveness of one of these games (called “ABCmouse”).

· Methods: She gave kids experience with ABCmouse or a noneducational game called “Pig Pile” then tested their reading ability

· All children were between the ages of 3-5 and were recruited from a large, public preschool

· The children were given 2 weeks to play their respective game, and then the researcher tested their reading ability using the Burt Reading Test

· The Burt Reading Test tests how many of 110 words a child can read (the words are graded in order of difficulty, so the more words a child can read, the better their score)

Questions:

· What is the independent variable (IV) in the Simple Experiment above? How many levels/conditions does the IV have?

· Independent Variable:

· Levels/conditions:

· What is the dependent variable (DV) in the Simple Experiment above? How was It operationalized?

· Dependent Variable:

· Operationalized:

Experiment Variation #1:

· Background: As it turned out, the Pig Pile game was considered inappropriate for school use by many of the teachers and, therefore, the researchers simplified their study and got rid of the Pig Pile game.

· New Study Design/Method: Early in the spring, kids in three targeted classrooms were tested on the Burt Reading Test

· Then after a month, during school hours, research assistants (RAs) introduced the ABCmouse game to each child who had permission to participate.

· For the next 2 weeks, during each morning’s play period, kids were required to play with this game for 10 minutes.

· At the end of this 2-week period, the Burt Reading Test was administered.

· Results: The mean reading score of the kids had risen (and the change was statistically significant) so the researchers concluded that ABCmouse improved kids’ ability to read words.

Questions:

· Multiple Choice: What is the experimental design of Variation #1? You can highlight your choice below!

A. pretest-posttest

B. posttest only

C. repeated measures

D. concurrent measures

E. one group, pretest-posttest

· Identify at least one threat to internal validity in Variation #1 (use Table 11.1 in your book/slides to help you out – there is at least one main threat for each of these variations). For the threat, name the threat and explain how internal validity is threatened (this can be bulleted!)

· Threat:

· How does this Variation #1 show this threat?:

Experimental Variation #2

· Background: Because the classroom sizes of all the 3 to 5-year-old groups were exactly the same, the researchers decided to have all of Miss Johnson’s kids be in the ABCmouse group and all of Miss Harris’s kids be in the Pig Pile group.

· Method : At the beginning of the study, all the kids were tested on the Burt Reading Test, and both of the classrooms had the same mean score.

· Then, during school hours, research assistants (RAs) introduced the appropriate games to each child.

· For the next 2 weeks, during each morning’s play period, kids were required to play with their respective game for 10 minutes.

· At the end of the 2 weeks, the Burt Reading Test was administered.

· Results : The mean reading score for kids in the ABCmouse was significantly higher than the reading score for the Pig Pile kids. The researchers concluded that ABCmouse improved kids’ ability to read words.

Questions:

· Multiple Choice: What is the experimental design of Variation #2? You can highlight your choice below!

A. pretest-posttest

B. posttest only

C. repeated measures

D. concurrent measures

E. one group, pretest-posttest

· Identify at least one threat to internal validity in Variation #2. For the threat, name the threat and explain how internal validity is threatened (this can be bulleted!)

· Threat:

· How does this Variation #2 show this threat?:

Experimental Variation #3:

· Background: The head of school sent out a letter describing the study’s goals to all of the children’s parents. She gave parents 2 weeks to return the consent forms.

· Methods: For convenience, she assigned the first parents to send back their forms to the ABCmouse group, and assigned later parents to the Pig Pile group.

· During school hours, research assistants (RAs) introduced the appropriate games to each child, according to his or her group.

· Then, for the next 2 weeks, during each morning’s play period, kids were required to play with their respective game for 10 minutes.

· At the end of this 2-week period, the Burt Reading Test was administered.

· Results: The mean reading score for kids in the ABCmouse was significantly higher than the reading score for the Pig Pile kids. The researchers concluded that ABCmouse improved kids’ ability to read words.

Questions:

· Multiple Choice: What is the experimental design of Variation #3? You can highlight your choice below!

A. pretest-posttest

B. posttest only

C. repeated measures

D. concurrent measures

E. one group, pretest-posttest

· Identify at least one threat to internal validity in Variation #2. For the threat, name the threat and explain how internal validity is threatened (this can be bulleted!)

· Threat:

· How does this Variation #3 show this threat?: