ABSTRACT
Many studies undertaken in the behavioral sciences and related disciplines involve recording the value of a response variable for each subject under more than one condition, on more than one occasion, or both. The subjects may often be arranged in different groups, either those naturally occurring such as gender, or those formed by random allocation, for example, when competing therapies are assessed. Such a design is generally referred to as involving repeated measures. Three examples will help in getting a clearer picture of a repeated measures type of study.
Visual acuity data. This example is one already introduced in Chapter 2, involving response times of subjects using their right and left eyes when light was flashed through lenses of different powers. The data are given in Table 2.3. Here there are two within subject factors, eye and lens strength.
Field dependence and a reverse Stroop task. Subjects selected randomly from a large group of potential subjects identified as having field-independent or field-dependent cognitive style were required to read two types of words (color and form names) under three cue conditions—normal, congruent, and incongruent. The dependent variable was the time in milliseconds taken to read the stimulus words. The data are shown in Table 5.1. Here there are two within subjects factors, type and cue, and one between subjects factor, cognitive style. Field Independence and a Reverse Stroop Task
b1 Form |
b2 Color |
|||||
---|---|---|---|---|---|---|
Subject |
c 1 (N) |
c 2 (C) |
c 3 (I) |
c 1 (N) |
c 2 (C) |
c 3 (I) |
a 1 (Field Independent) |
||||||
1 |
191 |
206 |
219 |
176 |
182 |
196 |
2 |
175 |
183 |
186 |
148 |
156 |
161 |
3 |
166 |
165 |
161 |
138 |
146 |
150 |
4 |
206 |
190 |
212 |
174 |
178 |
184 |
5 |
179 |
187 |
171 |
182 |
185 |
210 |
6 |
183 |
175 |
171 |
182 |
185 |
210 |
7 |
174 |
168 |
187 |
167 |
160 |
178 |
8 |
185 |
186 |
185 |
153 |
159 |
169 |
9 |
182 |
189 |
201 |
173 |
177 |
183 |
10 |
191 |
192 |
208 |
168 |
169 |
187 |
11 |
162 |
163 |
168 |
135 |
141 |
145 |
12 |
162 |
162 |
170 |
142 |
147 |
151 |
a 2 (Field Dependent) |
||||||
13 |
277 |
267 |
322 |
205 |
231 |
255 |
14 |
235 |
216 |
271 |
161 |
183 |
187 |
15 |
150 |
150 |
165 |
140 |
140 |
156 |
16 |
400 |
404 |
379 |
214 |
223 |
216 |
17 |
183 |
165 |
187 |
140 |
146 |
163 |
18 |
162 |
215 |
184 |
144 |
156 |
165 |
19 |
163 |
179 |
172 |
170 |
189 |
192 |
20 |
163 |
159 |
159 |
143 |
150 |
148 |
21 |
237 |
233 |
238 |
207 |
225 |
228 |
22 |
205 |
177 |
217 |
205 |
208 |
230 |
23 |
178 |
190 |
211 |
144 |
155 |
177 |
24 |
164 |
186 |
187 |
139 |
151 |
163 |
Alcohol dependence and salsolinol excretion. Two groups of subjects, one with severe dependence and one with moderate dependence on alcohol, had their salsolinol excretion levels (in millimoles) recorded on four consecutive days (for those readers without the necessary expertise in chemistry, salsolinol is an alkaloid with a structure similar to heroin). Primary interest centers on whether the groups behaved differently over time. The data are given in Table 5.2. Here there is a single within subject factor, time, and one between subjects factor, level of dependence.
Salsolinol Excretion Rates (mmol) for Moderately and Severely Dependent Alcoholic Patients
Day |
||||
---|---|---|---|---|
Subject |
1 |
2 |
3 |
4 |
Group 1 (Moderate Dependence) |
||||
1 |
0.33 |
0.70 |
2.33 |
3.20 |
2 |
5.30 |
0.90 |
1.80 |
0.70 |
3 |
2.50 |
2.10 |
1.12 |
1.01 |
4 |
0.98 |
0.32 |
3.91 |
0.66 |
5 |
0.39 |
0.69 |
0.73 |
2.45 |
6 |
0.31 |
6.34 |
0.63 |
3.86 |
Group 2 (Severe Dependence) |
||||
1 |
2 |
3 |
4 |
|
7 |
0.64 |
0.70 |
1.00 |
1.40 |
8 |
0.73 |
1.85 |
3.60 |
2.60 |
9 |
0.70 |
4.20 |
7.30 |
5.40 |
10 |
0.40 |
1.60 |
1.40 |
7.10 |
11 |
2.50 |
1.30 |
0.70 |
0.70 |
12 |
7.80 |
1.20 |
2.60 |
1.80 |
13 |
1.90 |
1.30 |
4.40 |
2.80 |
14 |
0.50 |
0.40 |
1.10 |
8.10 |