The F test for comparing two normal variances: correct and incorrect calculation of the two-sided p-value?

This article illustrates that not all statistical software packages are correctly calculating a p-value for the classical F test comparison of two independent Normal variances. This is illustrated with a simple example, and the reasons why are discussed. Eight different software packages are considered

Insect biodiversity meets ecosystem function: differential effects of habitat and insects on carrion decomposition

1. Ecological processes are maintained in different environments by different species performing similar functional roles. Yet, little is known about the role of the environment in shaping insect biodiversity associated with a process that is ephemeral and patchy. 2. In this study, the mass loss of carrion in response to contrasting habitat types (grassland or tree) was quantified experimentally, as well as the presence, diversity and composition of insect assemblages. Differences in insect assemblages between these two habitats were also examined. 3. It was found that the presence of insects led to a doubling in mass loss, but that grassland or tree habitat type had no effect on this process. By contrast, habitat type had a significant effect on the composition of generalist ant and beetle assemblages, but not on specialist fly assemblages. Given the colonisation of insects, carrion mass loss was negatively associated with increasing evenness of fly assemblages and increasing ant abundance. Variation in fly assemblage composition was also found to correlate with variation in carrion mass loss. 4. This study highlights the major role of habitat type in shaping the composition of generalist insects at carrion, but the minor role in affecting specialist and highly vagile insects. This complements the authors' findings that insect colonisation of carrion was critical to accelerated mass loss, and that fly assemblages were responsible for variation in this process, regardless of habitat. The present study sheds new light on the contribution of insect biodiversity to decomposition in variable environments, with consequences for carrion food webs and nutrient cycling. © 2017 The Royal Entomological Societ

Agronomic and quality attributes of worldwide primitive barley subspecies

Old barley germplasm from the primary gene pool (landraces and wild relative) provides a broad representation of natural variation not only in agronomically important traits but also in nutraceuticals. Five hundred and twenty barley landraces including 36 wild barley relatives belonging to 33 countries were subject to agronomic and quality screening. The mean values for the four implemented environments (two sites by 2 years) revealed that the subspecies H. spontaneum was a great source of important traits (spike length, plant height, protein content and β-glucan content) comparing to H. vulgare (the top in grain yield and heading date) and H. distichon (first in TKW and particle size index). The blue aleurone colour was dominated for the most studied accessions. The ANOVA between subspecies associated with canonical variate analysis and hierarchical clustering confirms the finding to be used in barley breeding through incorporation of the candidate gene into the commercial varieties