<abstract xmlns="http://www.w3.org/1999/xhtml"> Summary The main estimation and hypothesis testing results are presented for experiments conducted in proper block designs. It is shown that, under appropriate randomization, these experiments have the convenient orthogonal block structure. Because of this, the analysis of experimental data can be performed in a comparatively simple way. Certain simplifying procedures are introduced. The main advantage of the presented methodology concerns the analysis of variance and related hypothesis testing procedures. Under the adopted approach one can perform them directly, not by combining results from intra-block and inter-block analyses. Application of the theory is illustrated by three examples of real experiments in proper block designs. This is the first of a projected series of papers concerning the analysis of experiments with orthogonal block structure.</abstract>

On a New Approach to the Analysis of Variance for Experiments with Orthogonal Block Structure.

<abstract xmlns="http://www.w3.org/1999/xhtml"> We construct an incomplete split-block design (ISBD) by the semi- Kronecker product of two affine α-resolvable designs for row and column treatments. We characterize such ISBDs with respect to the general balance property and we give the stratum efficiency factors for the ISBDs.</abstract>

Incomplete split-block designs constructed by affine α-resolvable designs

<abstract xmlns="http://www.w3.org/1999/xhtml"> In this paper we study a certain kind of experimental designs called chemical balance weighing designs. We consider issues with regard to determining optimality conditions. We give new classes of designs in which we are able to determine an optimal design. Moreover, examples are given for the presented cases.</abstract>

Some D-optimal chemical balance weighing designs: theory and examples

<abstract xmlns="http://www.w3.org/1999/xhtml"> An application of semi-Markov models to AIDS disease progression was utilized to find best sojourn time distributions. We obtained data on 370 HIV/AIDS patients who were under follow-up from September 2008 to August 2015, from Yirgalim General Hospital, Ethiopia. The study reveals that within the “good” states, the transition probability of moving from a given state to the next worst state has a parabolic pattern that increases with time until it reaches a maximum and then declines over time. Compared with the case of exponential distribution, the conditional probability of remaining in a good state before moving to the next good state grows faster at the beginning, peaks, and then declines faster for a long period. The probability of remaining in the same good disease state declines over time, though maintaining higher values for healthier states. Moreover, the Weibull distribution under the semi-Markov model leads to dynamic probabilities with a higher rate of decline and smaller deviations. In this study, we found that the Weibull distribution is flexible in modeling and preferable for use as a waiting time distribution for monitoring HIV/AIDS disease progression.</abstract>

Comparison of Sojourn Time Distributions in Modeling HIV/AIDS Disease Progression

<abstract xmlns="http://www.w3.org/1999/xhtml"> This paper discusses the problem of determining the number of observations necessary to apply the nonparametric Mann-Whitney test. We describe the method given by Noether (1987) for determining a sample size which guarantees that the Mann-Whitney test at a given significance level α has a predetermined power 1-β. The presented theory is tested by calculating the empirical power in computer simulations. The paper also raises the issue of the method of rounding the determined sample size to an even number when the sample is divided into two equinumerous subsamples.</abstract>

Sample size determination in the Mann–Whitney test

<abstract xmlns="http://www.w3.org/1999/xhtml"> Excessive compaction of soil has an adverse effect on its aggregate structure, and as a result also on the yields of various crops. To prevent this negative impact, diverse methods of limited tillage are applied. However, these methods are not effective when cultivating sandy soils of very low natural porosity. An original integrated tillage method for such soils has been developed at the Poznań University of Life Sciences. This paper presents a comparison of yields and quality of three popular potato cultivars following the application of conventional and integrated tillage methods. The experiment shows that integrated tillage contributes to an increase in potato yield by providing better conditions for tuber growth.</abstract>

The effect of integrated tillage of light soil on potato yields

<abstract xmlns="http://www.w3.org/1999/xhtml"> The latest global economic and financial crisis has had adverse social consequences in many areas, including income and the social situation of households and their living conditions, especially when the housing phenomenon is addressed. The reality of this uncertainty has made the study of the housing phenomenon even more relevant, in particular from the perspective of an analysis of its evolution. In this context, we revisit EUROSTAT’s databases. This analysis was done for twelve Euro Area countries over five years, using the HJ-BIPLOT method developed by Galindo (1986). This multidimensional approach identified and represented twelve Eurozone sample countries in latent constructs of reduced dimensionality related to the housing policy problem. The simultaneous factorial representation identified (a) the most relevant variables to characterize these countries, (b) their trajectories during the period in analysis, and (c) the relations between variables, between countries, and between variables and countries. This approach also identified the most significant factors contributing to the countries' performance. This methodological approach can be useful in housing research, when studying data of a multivariate nature, and is also, by its visual interpretation, a potential tool for producing richer information not only for academia but also for policy makers.</abstract>

A Multidimensional Analysis of Socioeconomic Factors in Housing Policy in the Eurozone Countries (2010–2014)

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Biometrical Letters

 Biometrical Letters is the official journal of the Polish Biometric Society, founded in 1964, now published with the financial support of the Ministry of Science and Higher Education. The anonymous double-blind peer review by the two independent reviewers is applied to all the papers.  The purposes of Biometrical Letters are:   publishing papers dealing with various aspects of the analysis and interpretation of results from biometrical experiments, using mathematical and statistical methods;  promoting and extending the use of statistical and mathematical methods in the principal disciplines of life sciences by reporting on the development and application of these methods;  presenting statistical and mathematical tools useful in biometry. Methodological developments should be motivated by interesting problems from life sciences, applied or applicable;  publishing review papers and papers presenting practical use of various methods of data analysis and statistical inference.   The core of most Biometrical Letters articles is statistical inference that sets scientific or policy objectives, motivates methodological development and demonstrates the operation of new methods.  The paper should include a description of the biometrical problem and a section detailing the application of the new methodology.  The Journal welcomes the submission of manuscripts from bioscience, mathematical and statistical theory, biology, genetics, medical statistics, agriculture, forestry, ecology, environmental sciences, biometrics and clinical trials. Case studies and articles on the use and development of statistical software are also welcome.  Rejection Rate   20%   Archiving  Sciendo archives the contents of this journal in Portico - digital long-term preservation service of scholarly books, journals and collections.  Plagiarism Policy  The editorial board is participating in a growing community of Similarity Check System's users in order to ensure that the content published is original and trustworthy. Similarity Check is a medium that allows for comprehensive manuscripts screening, aimed to eliminate plagiarism and provide a high standard and quality peer-review process. 