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      Conclusions beyond support: overconfident estimates in mixed models

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          Abstract

          Mixed-effect models are frequently used to control for the nonindependence of data points, for example, when repeated measures from the same individuals are available. The aim of these models is often to estimate fixed effects and to test their significance. This is usually done by including random intercepts, that is, intercepts that are allowed to vary between individuals. The widespread belief is that this controls for all types of pseudoreplication within individuals. Here we show that this is not the case, if the aim is to estimate effects that vary within individuals and individuals differ in their response to these effects. In these cases, random intercept models give overconfident estimates leading to conclusions that are not supported by the data. By allowing individuals to differ in the slopes of their responses, it is possible to account for the nonindependence of data points that pseudoreplicate slope information. Such random slope models give appropriate standard errors and are easily implemented in standard statistical software. Because random slope models are not always used where they are essential, we suspect that many published findings have too narrow confidence intervals and a substantially inflated type I error rate. Besides reducing type I errors, random slope models have the potential to reduce residual variance by accounting for between-individual variation in slopes, which makes it easier to detect treatment effects that are applied between individuals, hence reducing type II errors as well.

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          R: A language and environment for statistical computing

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            Application of random regression models in animal breeding

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              • Record: found
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              • Article: not found

              Sex-specific effects of yolk-androgens on growth of nestling American kestrels

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                Author and article information

                Journal
                Behav Ecol
                beheco
                beheco
                Behavioral Ecology
                Oxford University Press
                1045-2249
                1465-7279
                Mar-Apr 2009
                27 November 2008
                27 November 2008
                : 20
                : 2
                : 416-420
                Affiliations
                Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, PO Box 1564, 82305 Starnberg (Seewiesen), Germany
                Author notes
                Address correspondence to H. Schielzeth. E-mail: schielz@ 123456orn.mpg.de .
                Article
                10.1093/beheco/arn145
                2657178
                19461866
                06d77b33-b170-49e4-937d-31e0c2373bcd
                © 2008 The Authors

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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