Research Designs
Researchers were interested in learning the effects of trans fats on levels of cholesterol in the blood. Two different research designs were constructed.
Between-Groups Design
In the between-groups design, researchers were interested in whether cholesterol levels would differ depending on diet. Twenty participants were randomly assigned to one of two different groups. Group A was assigned a diet rich in fruits and vegetables and with no trans fats. Group B participants were asked to follow their normal diets, which contained varying levels of trans fats depending on the individual. After one month, blood samples were drawn and the following levels of cholesterol were obtained:
Participant
Blood Cholesterol
Diet
1
129
Healthy
2
98
Healthy
3
150
Healthy
4
75
Healthy
5
135
Healthy
6
175
Healthy
7
115
Healthy
8
103
Healthy
9
156
Healthy
10
143
Healthy
11
239
Normal
12
500
Normal
13
350
Normal
14
468
Normal
15
198
Normal
16
213
Normal
17
225
Normal
18
175
Normal
19
560
Normal
20
289
Normal
Within-Subjects Design
In the within-subjects design, researchers were interested in whether participants could lower their cholesterol levels by changing from a diet higher in trans fats to one with no trans fats. Ten research participants were selected. A baseline measure of cholesterol was taken from each. They were then put on a diet rich in fruits and vegetables and devoid of trans fats for one month. At the end of that month, blood cholesterol was again measured, and the following results were obtained:
Participant
Blood Cholesterol
Diet
1
129
Baseline
1
98
Healthy
2
150
Baseline
2
75
Healthy
3
175
Baseline
3
135
Healthy
4
115
Baseline
4
103
Healthy
5
156
Baseline
5
143
Healthy
6
500
Baseline
6
450
Healthy
7
468
Baseline
7
350
Healthy
8
198
Baseline
8
213
Healthy
9
225
Baseline
9
175
Healthy
10
560
Baseline
10
481
Healthy
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In a Microsoft Word document, answer the following questions:
- What is the independent variable in the study for a Between-Subject Design? What are the levels of that independent variable? What is the dependent variable?
- What is the independent variable in the study for a Within-Subject Design? What are the levels of that independent variable? What is the dependent variable?
- Name this document SU_PSY2008_W5_A_ LastName_FirstInitial
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Based on what you learned in your lecture on Data Files for Between- and Within-Subject Designs , create a data file in Microsoft Excel that will enable you to conduct a between-subject analysis of this data.
- On a separate tab within your Microsoft Excel file (click the + sign at the bottom to create a new worksheet) create a data file that will enable you to conduct a within-subjects’ analysis of this data.
