| Classic experimental design |
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| Classic |
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| experimental |
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| design |
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| Time |
| Pretest |
| Posttest |
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| Experimental |
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| group |
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| R |
| O1 |
| X |
| O2 |
| O2-O1=de |
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| Control |
|
| group |
|
| R |
| O3 |
| O4 |
| O4-O3=dc |