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84 CHAPTER 4 Statistical analysis

participants with disabilities or specific expertise. To address that problem, you may
decide to use a within-group design, in which case you recruit just one group of par-
ticipants and have each participant complete the tasks under all conditions.
Repeated measures ANOVA tests can involve just one level or multiple levels.
A one-way, repeated measures ANOVA test can be used for within-group studies
that investigate just one independent variable. For example, if you are interested
only in the impact of the text entry method, a one-way, repeated measures ANOVA
test would be appropriate for the data analysis. If you use SPSS to run the test, the
three data points contributed by each participant should be listed in the same row.
Table 4.11 demonstrates the sample data layout for the analysis.

Table 4.11 Sample Data for One-Way, Repeated Measures ANOVA
Standard Prediction Speech
Participant 1 245 246 178
Participant 2 236 213 289
Participant 3 321 265 222
Participant 4 212 189 189
Participant 5 267 201 245
Participant 6 334 197 311
Participant 7 287 289 267
Participant 8 259 224 197

Table 4.12 is the simplified summary table for the one-way, repeated measures
ANOVA test generated by SPSS. The returned F value with degree of freedom
(2, 14) is 2.925. It is below the 95% confidence interval, suggesting that there is no
significant difference between the three text entry methods.

Table 4.12 Result of the One-Way, Repeated Measures ANOVA Test
Source Sum of Square df Mean Square F Significance
Entry method 7842.25 2 3921.125 2.925 0.087
Error 18,767.083 14 1340.506

Multiple-level, repeated measures ANOVA tests are needed for within-group
studies that investigate two or more independent variables. If you are interested in
the impact of both the text entry method and the types of task, the study involves six
conditions as illustrated in Table 4.13. A two-way, repeated measures ANOVA test
can be used to analyze the data collected under this design.

Table 4.13 Experiment Design of a Two-Way, Repeated Measures ANOVA Test

Standard Prediction Speech
Transcription Group 1 Group 1 Group 1
Composition Group 1 Group 1 Group 1