The devil lies in details: reply to Stuart Hurlbert
As pointed out in Stuart Hurlbert's recent article, ecologists still at times design their experiments sloppily, creating a situation where various forms of 'non-demonic intrusion' could account for the documented contrasts between treatments and controls. If such contrasts are nevert...
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Published in: | Oikos 2004-03, Vol.104 (3), p.598-605 |
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Main Author: | |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | As pointed out in Stuart Hurlbert's recent article, ecologists still at times design their experiments sloppily, creating a situation where various forms of 'non-demonic intrusion' could account for the documented contrasts between treatments and controls. If such contrasts are nevertheless presented to the reader as if they were statistically demonstrated treatment effects, then pseudoreplication is not a pseudoissue and the use of a stigmatizing label of is entirely warranted, as pointed out by Hurlbert. The problems with Hurlbert's concepts start in the context of studies, where the scope of the experiment is to provoke a chain of dramatic and a priori extremely unlikely events, which a given conjecture predicts to happen as a consequence of a given manipulation. As the essence of these experiments is to trigger large dynamical responses in a biological system, they often require much space and/or special conditions, allowing for efficient isolation of the experimental system from potential sources of contamination. These constraints can be incompatible with standard designs (randomization, replication and treatment-control interspersion). In the context of experiments, where it has been necessary to sacrifice randomization, replication or treatment-control interspersion, the logic of inferring treatment effects is the same as used when interpreting causes of spontaneous events or events triggered by manipulations with practical purposes. The observed contrasts can be reasonably interpreted as effects of the treatment if and only if their magnitudes and the timing of their emergence makes alternative explanations utterly implausible (which is up to the reader to judge). If the logic of inference is clearly explained and no claim of statistically demonstrated treatment effect is made, the use of stigmatizing labels like 'pseudoreplication' is unwarranted. However, it might clarify the literature if such imperfectly designed experiments are referred to as experimental events, to be distinguished from perfectly designed experiments, where mechanical interpretation of contrasts between treatments and controls as treatment effects can be regarded as socially acceptable. |
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ISSN: | 0030-1299 1600-0706 |
DOI: | 10.1111/j.0030-1299.2004.13266.x |