Term
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Definition
| Sometimes, just the passage of time results in people changing, even without any external cause |
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Term
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Definition
| Sometimes, the act of measurement itself at pretest can change behavior at posttest (even without any manipulation of the independent variable) |
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Term
| Instrument Decay or Instrumentation. |
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Definition
| Sometimes, the measurement instrument changes in a systematic way from pretest to posttest (a systematic bias in measurement), producing apparent differences when there are really none |
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Term
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Definition
| Sometimes, you lose (or gain) people between pretest and posttest, and this change in the composition of the sample itself can produce changes on the dependent variable |
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Term
| comparison, control, and manipulation |
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Definition
| Three concepts underlie scientists’ ability to find causal relationships |
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