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The testing for an association between two categorical variables using count data is commonplace in the behavioral sciences.
Here, we present evidence that influential biostatistical textbooks give contradictory and incomplete advice on good practice
in the analysis of such contingency table data. We survey the statistical literature and offer guidance on such analyses.
Specifically, we call for greater use of exact testing rather than tests which use an asymptotic chi-squared distribution.
That is, we suggest that researchers take a conservative approach and only perform asymptotic testing where there is little
doubt that it is appropriate. We recommend a specific criterion for such decision-making. Where asymptotic testing is appropriate,
we recommend chi-squared over the G-test and recommend against the implementation of Yates (or any other) correction. We also
provide advice on the effective use of exact testing for associations in contingency tables. Lastly, we highlight issues that
need to be considered when using the commonly recommended Fisher’s exact test. 相似文献
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Both the activity of phenoloxidases and the availability of phenoloxidase substrates are said to regulate melanotic encapsulation
in invertebrates. The delayed induced resistance of mountain birches has been shown to increase the immunity of Epirrita autumnata (Geometridae: Lepidoptera), but the mechanism behind the increased immunity is unknown. The increase in the contents of aromatic
amino acids as a response to herbivory in plants can in theory be one explanation for this carry-over effect. To test this
hypothesis that an increase in the substrate availability increases also the melanotic encapsulation rate and the immunity
of E. autumnata, we supplied excess levels of two aromatic amino acids, tyrosine (l-Tyr) and phenylalanine (l-Phe), to the diet of moth larvae. Surprisingly, the supply of both aromatic amino acids down-regulated PO activity, whereas
the melanotic encapsulation rate was maintained at an unchanged level. PO activity was traded-off with body size and thus
the cost of resistance is a probable explanation for the down-regulation of PO activity in the presence of surplus substrates.
Our results suggest that both aromatic amino acids act as substrates of melanin, and an increase in substrate contents allows
insects to decrease their PO activity without affecting the encapsulation rate. 相似文献
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M Martínez-Córcoles M Schöbel FJ Gracia I Tomás JM Peiró 《Journal of Safety Research》2012,43(3):215-221
IntroductionSafety participation is of paramount importance in guaranteeing the safe running of nuclear power plants.MethodThe present study examined the effects of empowering leadership on safety participation.ResultsBased on a sample of 495 employees from two Spanish nuclear power plants, structural equation modeling showed that empowering leadership has a significant relationship with safety participation, which is mediated by collaborative team learning. In addition, the results revealed that the relationship between empowering leadership and collaborative learning is partially mediated by the promotion of dialogue and open communication.ConclusionsThe implications of these findings for safety research and their practical applications are outlined.Impact on IndustryAn empowering leadership style enhances workers' safety performance, particularly safety participation behaviors. Safety participation is recommended to detect possible rule inconsistencies or misunderstood procedures and make workers aware of critical safety information and issues. 相似文献
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