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Full-Text Articles in Life Sciences
Paired Competition Analysis Using Mixed Models, Patrick Gallagher, Bruce A. Craig, Tim Luttermoser, Grzegorz Buczkowski
Paired Competition Analysis Using Mixed Models, Patrick Gallagher, Bruce A. Craig, Tim Luttermoser, Grzegorz Buczkowski
Conference on Applied Statistics in Agriculture
Urban and rural colonies of odorous house ants (Tapinoma sessile) have very different social structures. Urban colonies are very large with hundreds of cohabiting queens, while rural colonies are small with only one queen. To investigate whether worker ant aggressiveness varies across these two colony types, an experiment was performed using an aggression assay, in which 50 ants from each of two colonies were placed in a petri dish and allowed to fight. The response was the total number of dead ants within 24 hours. Because the ants were all the same species and not marked by colony, …
Should Blocks Be Fixed Or Random?, Philip Dixon
Should Blocks Be Fixed Or Random?, Philip Dixon
Conference on Applied Statistics in Agriculture
Many studies include some form of blocking in the study design. Block effects are rarely of intrinsic interest; instead they are included in a model so that that model reflects the study design. I consider the question of how these block effects should be modeled: as fixed effects or as random effects. I discuss the consequences of the choice, including the recovery of inter-block information when available, give a simple example to illustrate the connection between recovery of inter-block information and pooling two estimators of a treatment effect, and give an example where fitting a model with random block effects …