week4 lab


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

  1. 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
  2. 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.