Marcin Kozak

• PhD
• Professor (Associate) at University of Information Technology and Management in Rzeszow

We analyse labour demand and mismatch for educational traits in information and communication technology (ICT) occupations, taking into account the areas of education, occupations and skills in demand, and the supply of labour. We based our analysis on almost 40 million online job offers and a CAWI survey of people aged 18–65 in Poland. The analysi...

Coniferous trees and shrubs growing in natural stands are important reservoirs of naturally-occurring predators belonging to the family Phytoseiidae (Mesostigmata: Phytoseioidea). The fauna of these mites on eight native coniferous species in Poland was surveyed and an exploratory statistical investigation was carried out into mite-conifer associat...

Simple Summary Amblyseius andersoni (Chant) is a predatory mite frequently used as a biocontrol agent against phytophagous mites in greenhouses, orchards and vineyards. In Europe, it is an indigenous species, commonly found on various plants, including conifers. The present study examined whether A. andersoni can develop and reproduce while feeding...

The study identifies repeated offenders of scientific misconduct among authors affiliated to Indian institutions. To do so, we searched the SCOPUS database for retraction notices of articles written or co-written by such authors. Among them, we identified those who authored or co-authored more than one retracted article. The number of such authors...

ANOVA, one of the most common statistical methods applied in agronomy, offers a variety of results we can report when analyzing designed experiments. The focus, of course, is on treatment means, but what should we report to characterize precision? Should we choose treatment standard deviations (SDs) or standard errors of the mean or standard errors...

Objective: The study aims to compare the effectiveness of individual and group nutrition education methods in improving key anthropometric and biochemical markers in drug-treated, overweight-obese hypertensive adults. Methods: The randomized trial included 170 patients with pharmacologically well-controlled primary hypertension and body mass ind...

image Repeated measures of the height of willow plants can be made and analysed.

The internet services market in tourism is developing intensively. Among factors affecting the quality of hotel services, modern information technologies play an important role, so hotels need to adapt to this dynamically changing virtual environment. Since more and more Internet users use mobile devices, hotels should make their websites work with...

There is an increasing need for analysing the demand for skills in the labour market. While most studies aggregate skills in groups or use available proxies for them, the authors analyse the demand by employers for individual competences. Such an analysis better reflects reality because companies usually require job candidates to have particular co...

An increasing problem throughout the world, plagiarism and related dishonest behaviors have been affecting Indian science for quite some time. To curb this problem, the Indian government has initiated a number of measures, such as providing plagiarism detecting software to all the universities for free. Still, however, many unfair or incorrect pape...

This document provides R and SAS code for performing the interval-censored data analyses in Onofri, A., Piepho, H.P., Kozak, M. (2019): Analyzing interval-censored data in agricultural research: A review with examples and software tips. Annals of Applied Biology 174, 3-13.

Metric data are usually assessed on a continuous scale with good precision, but sometimes agricultural researchers cannot obtain precise measurements of a variable. Values of such a variable cannot then be expressed as real numbers (e.g., 1.51 or 2.56), but often can be represented by intervals into which the values fall (e.g., from 1 to 2 or from...

Biographical articles in scientific journals offer a platform for the commemoration of distinguished individuals from the world of science. Despite so important a role for the scientific community, research on biographical articles is scarce. To fill this gap, we have analyzed 190,350 biographical articles indexed in Web of Science, written by 251,...

Consider a field experiment laid out in a randomized complete block design in which you study three types of fertilizers for two winter wheat cultivars. One year, one location – the experiment is not repeated. You design it and then spend a lot of time and money to conduct it. You cultivate the soil and take care of the plants; you worry about them...

We consider two questions important for applying analysis of variance (ANOVA): Should normality be checked on the raw data or on the residuals (or is it immaterial which of the two approaches we take)? Should normality and homogeneity of variance be checked using significance tests or diagnostic plots (or both)? Based on two examples, we show that...

Correlation analysis is one of the most popular statistical methods. Despite that, the way research reports correlation is often misleading. The difficulty increases with the amount of information that must be read and interpreted. The proposed CI thermometer makes correlation matrices much easier to read and provides information that would be diff...

Survey statisticians use either approximate or optimisation-based methods to stratify finite populations. Examples of the former are the cumrootf (Dalenius & Hodges, 1957) and geometric (Gunning & Horgan, 2004) methods, while examples of the latter are Sethi (1963) and Kozak (2004) algorithms. The approximate procedures result in inflexible stratum...

Data visualization helps analyze and present scientific data. In agricultural sciences, mainly bar charts – and less often scatterplots and pie charts – are used to visualize data. Too rarely more advanced types of plots are used, even though in many situations they offer richer interpretation than the simple types of plots. The paper deals with th...

Even though data visualization is a common analytical tool in numerous disciplines, it has rarely been used in agricultural sciences, particularly in agronomy. In this paper, we discuss a study on employing data visualization to analyze a multiplicative model. This model is often used by agronomists, for example in the so-called yield component ana...

Chemical analysis of healthy leaves of Tilia cordata Mill., T. platyphyllos L. and T. tomentosa Moench and leaves infested by eriophyoid mites was carried out to compare the nutrient values of the Tilia species for Eriophyes exilis (Nalepa), E. nervalis (Nalepa) and Phytoptus tetratrichus Nalepa. Concentrations of sugars, proteins and phenols in le...

Modern agricultural research requires a lot of statistics. Unfortunately, most up-to-date statistical methods need advanced knowledge, often out of reach for agricultural research­ers. Thus, efficient communication between researchers and statisticians is important for the development of agricultural knowledge. Many agricultural researchers claim t...

Morphology and anatomy of the root system of new potato cultivars Part II. Root anatomy  Morfologia i anatomia systemu korzeniowego nowych odmian ziemniaka Część II. Anatomia korzeni The comparison of primary adventitious roots structure was done in a survey study of 17 Solanum tuberosum cultivars differently tolerant to drought by means of micros...

International collaboration is becoming more important for modern science. Among others, it is reflected in authorships of scholarly articles. We studied internationality of Current Science based on internationality of its authors. We analysed articles based on their authors, taking into account foreign authors, co-authorship between countries. We...

Analiza danych z wykorzystaniem wizualizacji przy pomocy różnego rodzaju wykresów zyskuje coraz większe uznanie w świecie badaczy z różnych dziedzin nauki między innymi w szeroko pojętym rolnictwie, a szczególnie w ochronie roślin. Niestety ten sam wykres przez jednego czytelnika może być szybciej i lepiej zinterpretowany niż przez drugiego. To sam...

This paper provides a detailed description of Phyllocoptes adalius, eriophyoid species with a complex life cycle. P. adalius has recently become one of the most important mite pests in greenhouse rose production. We present morphometric data and illustrations that help to distinguish protogyne and deutogyne female forms. Both forms are differentiat...

Typhlodromus pyri Scheuten and Euseius finlandicus (Oudemans) are important predators of phytophagous mites. The present laboratory study aimed to determine whether both species can develop and reach maturity feeding on spider mites occurring on willows, i.e., Schizotetranychus schizopus (Zacher), Schizotetranychus garmani Pritchard & Baker, and Te...

Most yield progress obtained through the so called “green revolution”, particularly in the irrigated areas of Asia, has reached a limit, and major resistance genes are quickly overcome by the appearance of new strains of disease causing organisms. New plant stresses due to a changing environment are difficult to breed for as quickly as the changes...

Spam has become an issue of concern in almost all areas where the Internet is involved, and many people today have become victims of spam from publishers and individual journals. We studied this phenomenon in the field of scholarly publishing from the perspective of a single author. We examined 1,024 such spam e-mails received by Marcin Kozak from...

Delphi method, financial forecasting, structured discussion

Data input errors can potentially affect statistical inferences, but little research has been published to date on this topic. In the present paper, we report the effect of data input errors on the statistical inferences drawn about population parameters in an empirical study involving 280 students from two Polish universities, namely the Warsaw Un...

A pie chart is a common way of presenting simple statistics-for example, the amount of time devoted to teaching, researching, and administration by the faculty can be illustrated by dividing a circle ('pie') into three appropriately sized segments. There has been much discussion about the strengths and weaknesses of such pie charts for a long time,...

Obydwa wykresy przedstawiają trzy zmienne, jako składowe sumy: Zmienna A + Zmienna B + Zmienna C = 100% Podstawą obu wykresów są trójkąty: wykresu trójkątnego – trójkąt równoboczny, a wykresu trójkątno-prostokątnego-trójkąt prostokątny równoramienny, gdzie każdy wierzchołek wraz z odpowiednim bokiem trójkąta reprezentuje jedną zmienną (Wykres 1). P...

The grain proteins of barley are deficient in lysine and threonine due to their low concentrations in the major storage protein class, the hordeins, especially in the C-hordein subgroup. Previously produced antisense C-hordein transgenic barley lines have an improved amino acid composition, with increased lysine, methionine and threonine contents....

Whether one should use a public e-mail account (e.g., Gmail, Yahoo!) or an institutional one (e.g., @wsiz.rzeszow.pl, @medicine.ox.ac.uk) as an address for correspondence is an important aspect of scientific communication. Some authors consider that public e-mail services are unprofessional and insecure, whereas others say that, in a dynamically ch...

Studying relationships among plant and crop traits is crucial for crop scientists to understand complex biological systems that occur in plants and the field. Such knowledge constitutes the basis for more practical information on how to manage breeding and production to provide better or more suitable cultivars, higher yields, lower yield gaps, and...

The Tukey mean-difference plot, also called the Bland–Altman plot, is a recognized graphical tool in the exploration of biometrical data. We show that this technique deserves a place on an introductory statistics course by encouraging students to think about the kind of graph they wish to create, rather than just creating the default graph for the...

In light of the growing importance of web-based data in the social and behavioral sciences, WEBDATANET was established in 2011 as a COST Action (IS 1004) to create a multidisciplinary network of web-based data collection experts: (web) survey methodologists, psychologists, sociologists, linguists, economists, Internet scientists, media and public o...

This concise and readable set of editorial guidelines was first published by the European Association of Science Editors (EASE) in 2010 and is updated annually. It is freely available in more than 20 languages at http://ease.org.uk/publications/author-guidelines. The document is aimed to help scientists worldwide in successful presentation of their...

Many papers have appeared recently assessing the effects of using tables and graphs in scientific publica- tions. In this brief communication, we assess some of the methodological difficulties that have arisen in this context. These difficulties encompass issues of data availability, suitability of indicators, nature and purpose of tables and graph...

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 ori...

Beak and feather disease virus- (BFDV-) positive (naturally infected) but clinically healthy budgerigars (Melopsittacus undulatus) were inoculated with two isolates of Mycobacterium avium subsp. avium isolated from naturally infected golden pheasant (Chrysolophus pictus) and peafowl (Pavo cristatus). During a period of more than two months after in...

Multidisciplinary science journals include a few papers in economics. However, very few papers in economics appear in Current Science, itself a multidisciplinary journal. This article reports the results obtained from our analysis of the possible reasons for this situation. A study of almost 6500 articles from the journal's archives led us to the c...

Deficit irrigation agriculture is defined as the application of water below crop requirements. Water use efficiency is the main trait used to evaluate the efficiency of agriculture under deficit irrigation, determined as the harvested biomass per applied volume of water. Agriculture under deficit irrigation is based on the widely accepted belief th...

The biology of Phyllocoptes adalius Keifer (Acari: Eriophyoidea) and influence of insemination on female fecundity and longevity were studied. The experiment was conducted at a constant temperature of 25 ± 0.5 °C, 70–80 % RH and 16-h photoperiod. A modified method of mite rearing on detached leaves in closed cells was successfully applied and demon...

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 E...

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...

This note shows that the genetic algorithm proposed by Keskintürk and Er (Computational Statistics and Data Analysis 2007, 52, 53–67) usually provides similarly effective stratification to that of the random search algorithm proposed by Kozak (Statistics in Transition 2004, 6(5), 797–806), although in some situations it can be noticeably less effec...

In this article, we report on the status of graphs in 21 scientific agricultural journals indexed in Thomson Reuters’Web of Knowledge.We analyze the authors’ use of graphs in this context in relation to the quality of these journals as measured by their 2-year impact factors. We note a substantial variability in the use of graphs in this context: Fo...

Hedonic ranking is one of the commonly used methods to evaluate consumer preferences. Some authors suggest that it is the best methodology for discriminating among products, while others recommend hedonic rating. These mixed findings suggest the statistical outcome(s) are dependent on the experimental conditions or a user's expectation of “what is”...

Isozyme, RAPD and AFLP markers were evaluated and compared for their ability to determine genetic similarity in a set of 18 parental lines of winter oilseed rape F-1 hybrids developed using CMS ogura. Five isozyme systems, 64 RAPD starters and 23 EcoRI+3/MseI+3 AFLP primer combinations generated 597 polymorphic markers. These polymorphic fragments...

Three poorly known species of the subfamily Eriophyinae living on Tilia spp. (Tiliaceae) are illustrated and supplementary descriptions are provided. Two of them, Eriophyes exilis (Nalepa 1892) and Eriophyes nervalis (Nalepa 1918), were recorded both in vein angle galls on leaves of Tilia platyphyllos Scop. and in erinea on leaves of Tilia tomentos...

Parasitus bituberosus Karg (Acari: Parasitidae) is one of the predatory mite species inhabiting mushroom houses. It is known to accept a wide range of prey, suggesting that it may be a promising candidate for the biological control of key pests of mushroom culture. In our study it did not show any prey preference among four groups of small organism...

According to van Raan 1 , 'A "Sleeping Beauty in Science" is a publication that goes unnoticed ("sleeps") for several years and then, almost suddenly, attracts a lot of attention ("is awakened by a Prince").' Defined this way, a Sleeping Beauty describes a discovery that is ahead of its time and such papers get called Sleeping Beauties because of t...

The paper considers a problem of estimating a finite population parameter T (α, β, γ) in two-phase and successive sampling. Asymptotic optimum estimator (AOE) in a class is identified with its approximate variance formula. Several estimators of different parameters are identified as particular members of the class. In particular, we have focused on...

Fresh rhizomes of 21 genotypes of turmeric, including commercial cultivars and experimental genotypes, were assayed for curcuminodes content and antioxidant activity for two consecutive years. Curcumin was the most abundant curcuminode in all the genotypes, which occurred at concentrations ranging from 1.3 % to 4.5 % (with mean of 2.8 % ± standard...

We propose a wide class of estimators of the ratio of two finite-population means in the presence of random non response. Four estimators proposed by Toutenburg and Srivastava (1998) are shown as special cases of the proposed class of estimators. Linear models are developed to estimate the relative efficiency of the proposed class of estimators wit...

Harvest index describes plant capacity to allocate biomass (assimilates) into the formed reproductive parts; hence it is an important trait for plant breeding. Its relationships with biomass and grain yield follow the multiplicative yield component model, in which grain yield is a product of harvest index and biomass yield. In this paper a visualiz...

Coefficient of variation is very often used to describe variability in a variable. However, when the variable is studied in a factorial experiment, it can be used to determine pooled coefficient of variation, based on the variance of the residual term from an analysis of variance model. Such a coefficient disregards the variability that comes from...

This paper discusses a number of aspects concerning the analysis, interpretation and reporting of correlations in agricultural sciences. Various problems that one might encounter with these aspects are identified, and suggestions of how to overcome these problems are proposed. Some of the examples presented show how mistaken and even misleading the...

The population dynamics of the gall-inducing mites Phytoptus tetratrichus Nalepa and Eriophyes exilis Nalepa (Eriophyidae) on 50- to 60-year-old trees of Tilia tomentosa Moench, Tilia cordata Mill. and Tilia platyphyllos Scop. are presented. During the 2002–2004 growing seasons, two generations of protogynes and deutogynes occurred. The development...

Visitor's access to understorey vegetation in park forest stands results in the impoverishment of plant species composition and a reduction in habitat quality. The phenomenon of biotic homogenisation is typical in urban landscapes, but it can proceed differently depending on the scale, a detail that has not been observed in previous studies. This r...

In this paper we propose a new family of cumulative indexes for measuring scientific performance which can be applied to many metrics, including h index and its variants (here we apply it to the h index, h(2) index and Google Scholar's i10 index). These indexes follow the general principle of repeating the index calculation for the same publication...

R code for the indices used in the paper. (DOCX)

In many sciences, the relationships among the variables in multivariate data sets are often explored by means of correlation tables. In such studies there is often only one key variable of interest, for example, grain yield for cereals in agriculture, and class-size and academic performance in education. However, in such instances, there are no par...

This paper aims to provide insights into knowledge on morphology, biology and development of Megaselia halterata (Wood), one of the most common insect pests of mushroom houses. We focus on such traits as body length and weight and width of pseudocephalon, and show how these traits differ in subsequent development stages as well as across time. The...

A visit from Superman shows why data visualization should come before data analysis. The Web extra is a dataset that comprises 100 observations of the quantitative variables y and x plus the qualitative variable group. When analyzed correctly, this dataset exhibits an interesting pattern.

A text table is a simple table, with no or minimal chartlike elements, that is incorporated directly within a sentence. It can be very efficient in conveying quantitative (and sometimes qualitative) information that can be difficult to read within one or two sentences, but which is too simple to present within a regular table. Although this format...

Genetically modified organisms (GMOs) are a hot topic for debate among researchers from a wide range of scientific disciplines – in particular, agriculture, biotechnology and environmental protection. The debate, however, is not limited to science. GMOs are also discussed in the mass media, giving rise to extreme emotions, both positive and negativ...

Texts in agricultural and biological sciences are full of numbers, but far too often these numbers are not presented well. The way that numbers are reported does matter, as it can either help or hinder the reader in understanding the message. In particular, how many digits are chosen for each number is important. This choice should be governed by t...

The present research aimed to evaluate the effect of silver nitrate (AgNO3) on sex modification in sweet gourd (Momordica cochinchinensis Spreng.), and to explore the possibility of sexual crossing between two genetically female plants. Spray applications of AgNO3 on 30days’ old female plants induced hermaphrodite flowers. Male plants were insensit...

The purpose of this research was to investigate both the qualitative and quantitative morphological traits of Phytoptus tetratrichus Nalepa 1890 populations inhabiting three different lime tree species: Tilia cordata Mill., Tilia tomentosa Moench and Tilia americana L.. Morphological characters of two populations collected from T. cordata and T. to...

Far too often, phenotypic divergence has been misinterpreted as genetic divergence, and based on phenotypic divergence, genetic divergence has been indicated. We have attempted to disprove this statement and call for the differentiation of phenotypic and genotypic variation.

This article addresses an important problem of graphing quantitative data: should one include zero on the scale showing magnitude? Based on a real time series example, the problem is discussed and some recommendations are proposed.

Two methods are compared for univariate stratification of skewed population: geometric stratification and clustering through K-means algorithm. A simulation study for exponential distribution of the stratification variable revealed that geometric stratification was less efficient than the K-mean algorithm. In addition, quite often the strata the fo...

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 req...

Different authors in different disciplines conclude their articles in different ways. In this paper we illustrate this statement with examples and suggest that one particular way of clarifying the conclusions of articles in the sciences and social sciences is to print them using bullet points. We present as examples the conclusions from four papers...

Wykorzystanie diagramu łodyga i liście do analizy danych w środowisku R * Use of stem-and-leaf diagram for data analysis in R environment Szczególną rolę w analizie danych odgrywa badanie rozkładu zmiennych ilościowych; w tym celu najlepsze okazują się być techniki graficzne. Wśród bogatej oferty różnego rodzaju wykresów wykorzystywanych w tym celu...

Wizualizacja danych jest bardzo skutecznym narzędziem wspomagającym proces analizy danych rolniczych na każdym jej etapie, od zapoznawania się z danymi, poprzez interpretację zjawisk, aż po wnioskowanie. Często pozwala na skuteczne zaobserwowanie struktury danych czy obserwacji odstających lub nietypowych, które w innym wypadku trudno byłoby dostrz...

The bridge plot is used to visualize the famous Iris data. With the help of trellis system to condition the data on species, the plot presents four iris flower traits in their original units within a single panel. Such a plot can be employed when among four variables there are two groups each consisting of two variables having the same and comparab...

A web platform (http://www.animation.statgrafia.pl/correlation) accompanying a previous paper (Teach Stat 31 (2009), 52-54) is described. The platform contains animations of a small simulation study based on the population presented in the above-mentioned paper, results of a similar but large simulation study based on the same population, and resul...

Ash gourd is an important vegetable especially in the Indo-China region, but also in America and Africa. It is a monotypic genus, and its genetic pool is considered little diverse, which makes breeding of good ash gourd cultivars difficult. A pool of 56 genotypes, of which 10 are released cultivars and 46 indigenous lines collected from different p...

Causal inference methods--mainly path analysis and structural equation modeling--offer plant physiologists information about cause-and-effect relationships among plant traits. Recently, an unusual approach to causal inference through stepwise variable selection has been proposed and used in various works on plant physiology. The approach should not...

This study investigated whether the choice of a tillage system (no-tillage, minimum tillage or traditional tillage) affected weed diversity in a 23 years cereal–leguminous rotation system in Spain. Weed diversity was assessed using common diversity indices: species richness, Shannon's index and Pieloús evenness. Linear mixed-effects models were emp...

A proposed scatterplot design combines two other designs. One, proposed by Edward Tufte, uses the range-frame; the other, advised by William Cleveland, uses the four-scale-line rectangle. The hybrid design aims to present bivariate data with more information than classic scatterplots or Tufte's and Cleveland's designs. It works well for both single...

Genetically modified organisms (GMOs) are a hot topic for debate among researchers from a wide range of scientific disciplines – in particular, agriculture, biotechnology and environmental protection. The debate, however, is not limited to science. GMOs are also discussed in the mass media, giving rise to extreme emotions, both positive and negativ...

This paper offers a new method of inspecting associations in multivariate data sets, which is important when one wants to present a correlation table, frequent situation in agricultural sciences. We propose to use a simple visualization technique called the Bland-Altman plot for that, with a minor modification. The plot compares Pearson’s and Spear...

Concerns the correct citation of T. Caliński and J. Harabasz [Commun. Stat. 3, 1–27 (1974; Zbl 0273.62010)], where the first author is often misspelled as R. B. Caliński.

Adaptation can be studied through various methods, some of which are based on adaptation or stability measures while others on complex models and graphs. In this paper a simple adaptation measure based on quantiles is presented; the measure is three-dimensional and can be pictured with a ternary (trilinear) plot. A simple algorithm for constructing...

Adaptation can be studied through various methods, some of which are based on adaptation or stability measures while others on complex models and graphs. In this paper a simple adaptation measure based on quantiles is presented; the measure is three-dimensional and can be pictured with a ternary (trilinear) plot. A simple algorithm for constructing...

A G × E performance (interaction, profile) plot for showing genotype-by-environment data is discussed. Three versions of such a plot are compared: the regular performance plot; the performance plot based on coded data (environment-centered performance plot), in which the environment means of a trait are subtracted from data; and the performance plo...

Visualizing genotype-by-environment interaction in the case of several attributes, a situation that is often dealt with in plant breeding, is discussed in the paper. The parallel coordinate plot is proposed as an efficient tool for such visualization. Various applications of this type of graph are presented for across-environment and environment-wi...