Marcin Kozak

On Sample Allocation in Multivariate Surveys

The problem of a sample allocation between strata in the case of multiparameter surveys is considered in this article. There are several multivariate sample allocation methods and, moreover, several criteria to deal with in such a case. A maximum coefficient of variation of estimators of the population mean of characters under study is taken as the optimality criterion. This article contains a study on a group of the methods that are easy to implement and do not need complex numerical computation; however, they all are approximate. Five such methods are presented and compared using a simulation study. Finally, it is shown which methods should be considered when designing a survey in which the multivariate sample allocation is to be involved.

How have the Eastern European countries of the former Warsaw Pact developed since 1990? A bibliometric study

Did the demise of the Soviet Union in 1991 influence the scientific performance of the researchers in Eastern European countries? Did this historical event affect international collaboration by researchers from the Eastern European countries with those of Western countries? Did it also change international collaboration among researchers from the Eastern European countries? Trying to answer these questions, this study aims to shed light on international collaboration by researchers from the Eastern European countries (Russia, Ukraine, Belarus, Moldova, Bulgaria, the Czech Republic, Hungary, Poland, Romania, and Slovakia). The number of publications and normalized citation impact values are compared for these countries based on InCites (Thomson Reuters), from 1981 up to 2011. The international collaboration by researchers affiliated to institutions in Eastern European countries at the time points of 1990, 2000 and 2011 was studied with the help of Pajek and VOSviewer software, based on data from the Science Citation Index (Thomson Reuters). Our results show that the breakdown of the communist regime did not lead, on average, to a huge improvement in the publication performance of the Eastern European countries and that the increase in international co-authorship relations by the researchers affiliated to institutions in these countries was smaller than expected. Most of the Eastern European countries are still subject to changes and are still awaiting their boost in scientific development.

Selection of promising genotypes based on path and cluster analyses

The objective of the present paper was to propose a statistical approach to support selection of the most promising genotypes in a breeding programme. The approach is based on applying two state-of-the-art statistical methodologies, likelihood-based path analysis and model-based cluster analysis. The first method is applied to find a causal mechanism lying behind a biological process of development of final crop yield. These results are then used for weighting traits to be used in cluster analysis, which helps select genotypes possessing a desirable level of yield and yield-contributing traits. An application of the approach is presented for a 2-year study on 22 grasspea genotypes, two cultivars (Derek and Krab) and 20 mutants from those cultivars. Seed yield/plant and seven yield-related traits were studied. Among these, plant height, number of branches/plant, pod length and number of seeds/plant determined seed yield; number of pods/plant influenced seed yield only for 2002. These results were used for appropriate weighting in cluster analysis, which indicated that cultivar Krab and its two mutants, K3 and K64, had the best level of the traits and were the most stable genotypes.

Improved Estimation of Finite-Population Mean Using Sub-Sampling to Deal with Non Response in Two-Phase Sampling Scheme

This article proposes some alternative estimators for estimating the population mean of a study variable y using information on an auxiliary variable x in the presence of non response under two-phase sampling. The properties of the suggested estimators are given under a large-sample approximation, and the conditions are obtained in which the suggested estimators are better than the conventional unbiased estimators, usual two-phase sampling ratio, and product estimators. In addition, survey cost aspects are discussed under a linear cost function. A real agricultural population is used to present the application of the proposed estimators.

Publication fees for open access journals: Different disciplines—different methods

Many authors appear to think that most open access (OA) journals charge authors for their publications. This brief communication examines the basis for such beliefs and finds it wanting. Indeed, in this study of over 9,000 OA journals included in the Directory of Open Access Journals, only 28% charged authors for publishing in their journals. This figure, however, was highest in various disciplines in medicine (47%) and the sciences (43%) and lowest in the humanities (4%) and the arts (0%).

Analyzing one-way experiments: a piece of cake of a pain in the neck?

Realizar analises estatisticas pode ser complicado. Em situacoes praticas muitos pesquisadores utilizam os procedimentos de analise mais comuns, sem investigar se os mesmos sao apropriados para os seus resultados, ou mesmo se ha outros metodos que poderiam ser mais adequados. Nesse artigo buscarei mostrar que mesmo na analise de experimentos de classificacao simples (com um unico fator) varios aspectos precisam ser considerados. A forma classica de analise desse tipo de dados e a analise de variância, que e provavelmente o metodo estatistico mais usado na agricultura, biologia, ecologia e estudos de meio ambiente. Suspeito que essa e a razao pela qual tal metodo e frequentemente usado de forma inapropriada: uma vez que ele e muito usado, nao suscita maiores consideracoes. Imagino que seja esse raciocinio que muitos pesquisadores devam empregar. Analises incorretas podem fornecer falsas interpretacoes e conclusoes, e dessa forma e importante prestar atencao na escolha do procedimento a ser usado na analise. Nao estou sugerindo que algum metodo dificil ou complexo deva ser usado, mas sim que um metodo correto seja adotado, de forma a fornecer os resultados adequados. Dessa forma, varios problemas relacionados a analise de variância e outras abordagens para analisar esse tipo de dados sao discutidas nesse artigo, incluindo verificacoes de normalidade e homogeneidade de variâncias, analise de experimentos com violacao dessas pressuposicoes, presenca de dados discrepantes, testes de comparacoes multiplas, alem de alguns outros problemas.

Genetic and morphological diversity of Trisetacus species (Eriophyoidea: Phytoptidae) associated with coniferous trees in Poland: phylogeny, barcoding, host and habitat specialization

Eriophyoid species belonging to the genus Trisetacus are economically important as pests of conifers. A narrow host specialization to conifers and some unique morphological characteristics have made these mites interesting subjects for scientific inquiry. In this study, we assessed morphological and genetic variation of seven Trisetacus species originating from six coniferous hosts in Poland by morphometric analysis and molecular sequencing of the mitochondrial cytochrome oxidase subunit I gene and the nuclear D2 region of 28S rDNA. The results confirmed the monophyly of the genus Trisetacus as well as the monophyly of five of the seven species studied. Both DNA sequences were effective in discriminating between six of the seven species tested. Host-dependent genetic and morphological variation in T. silvestris and T. relocatus, and habitat-dependent genetic and morphological variation in T. juniperinus were detected, suggesting the existence of races or even distinct species within these Trisetacus taxa. This is the first molecular phylogenetic analysis of the Trisetacus species. The findings presented here will stimulate further investigations on the evolutionary relationships of Trisetacus as well as the entire Phytoptidae family.

Winter triticale grain yield, a comparative study of 15 genotypes

Abstract In the paper, we studied genotypic differences in the process of winter triticale grain yield formation, in terms of yield determination by its components. We applied yield component analysis on four dwarf and 11 traditional (conventional stature) genotypes; an ontogenetic approach was employed to provide the appropriate view of this process. Using the k-means clustering procedure, the genotypes were grouped subject to similar yield structure (i.e., mean values and coefficients of variation of grain yield and its components, first clustering), similar correlation matrices among grain yield and its components (second clustering), and similar results of yield component analysis (third clustering). Based on the analysis, we attempted to provide an overall general view of determining winter triticale grain yield by its components. Thus, we elucidate that the pattern of influencing winter triticale grain yield by its components, as well as the pattern of co-relationships among these traits, cannot be explained by yield structure, and hence these two processes are determined by genotypic factors. The correlation among the traits (grain yield and its components) and the results of yield component analysis, on the other hand, were significantly related in the study, so they have similar genotypic sources.

A heuristic method of searching for interesting markers in terms of quantitative traits

Selection of parental lines is important in plant breeding programmes. Marker-assisted selection is an alternative to classical selection methods, which are expensive and time consuming. Marker-assisted selection aims to find molecular markers that are linked to genes that determine quantitative traits of interest. Classical statistical methods require particular assumptions to be fulfilled, which is difficult to check if the analyses are performed automatically. In this article, we present a heuristic method to find interesting markers for quantitative traits. This method includes various strategies that depend on what makes a genotype interesting to a plant breeder. This approach was applied to eighteen parental lines of winter oilseed rape F1 CMS ogura hybrids with observation of 597 markers. The traits of interest were seed yield and alkenyl glucosinolate content. Fifty-seven markers were selected for further study. The most prominent marker was OPY 02~1830. Marker-assisted selection is the first step of analysis, which can then be followed up by a more formal statistical analysis for a smaller set of interesting markers.

Experimental infection of budgerigars (Melopsittacus undulatus) with five Mycobacterium species

The aim of the present study was to determine the susceptibility of budgerigars (Melopsittacus undulatus) to infections with different Mycobacterium species. For inoculations the following Mycobacterium species were used: Mycobacterium avium subsp. avium, Mycobacterium bovis subsp. bovis, Mycobacterium tuberculosis subsp. tuberculosis, Mycobacterium intracellulare and M. fortuitum subsp. fortuitum. The bacterial suspension was administrated intramuscularly and all the birds were monitored for 70 days starting from the day of inoculation. During the experiment clinical examination, X-ray scans, plate agglutination tests, tuberculin tests, faeces smear preparations and culture of mycobacteria were performed. The study showed that M. bovis subsp. bovis was the most pathogenic Mycobacterium species for budgerigars. After inoculation, the bacilli induced tuberculosis-typical, clinical signs and necropsy findings. In two out of six birds infected with M. bovis subsp. bovis radiological changes were also visible. Birds inoculated with other Mycobacterium species did not show any typical symptoms of infection, and only the results of histopathological and bacteriological examinations indicated the presence of infection.