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Fallacies |
| Experimenter Bias | ||
| Classification: An inductive fallacy of soundness in the Misrepresentations category. | ||
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| Description: The argument draws a conclusion from data that has been tainted (consciously or unconsciously) by the preferences of the person recording the data. Tainting of the data may be due to such mistakes as rounding up or rounding down to favor a certain result, or treating ambiguous results as favoring the preferred result. | ||
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| Example: | ||
| Samuel Morton collected data on cranial capacity, hoping to prove that white races had a larger brain size than dark races. He measured cranial capacity by filling the cranium with mustard seed and measuring how much seed each skull could hold. He performed the experiment himself, knowing which skulls belonged to whites and which belonged to blacks. His results confirmed an average cranial capacity of 87 cubic inches for whites, but only 83 cubic inches for Africans. | ||
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| Discussion | ||
| Since such tainting may be unconscious, steps must be taken to prevent it.
The fallacy of Experimenter Bias may be avoided by using "double blind"
techniques, so that experimenters do not know (as they are recording data) which result
the data favors. Any experiment that does not employ such techniques may be suspected
of committing the error of Experimenter Bias, so experimenters are generally very careful
to build such techniques into their experiment. Double blind means that both the experimenter and the experimental subject are "blind" to the meaning of the data being collected. Experiments in which the experimenter is not "blind" may commit the fallacy of Experimenter Bias; experiments in which the experimental subject are not "blind" commit the fallacy of Dishonest Sample. |
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