André Luís Santos de Pinho

The Error Structure of Split-Plot Experiments

#Edited by Søren Bisgaard.

Seasonal distribution of gastrointestinal nematode infections in sheep in a semiarid region, northeastern Brazil

The objective of this study was to determine the seasonal distribution and gastrointestinal nematode parasite load in crossbred Santa Inês tracer lambs, and to correlate the rainfall during the study period with occurrences of parasitic infections. Sixty-four male tracer lambs between the ages of four and eight months were used in the study. Two tracer lambs were inserted into the herd every 28 days to determine the pattern of infective larvae available in the environment. Variation in the fecal egg count (FEC) of nematodes was observed at the study site, with many samples containing undetectable parasite loads during the dry season. The larvae identified in coprocultures were Haemonchus sp., Trichostrongylus sp., Cooperia sp., Strongyloides sp. and Oesophagostomum sp. The nematodes recovered at necropsy were Haemonchus contortus, Trichostrongylus colubriformis, Cooperia punctata, C. pectinata, Trichuris sp., Oesophagostomum sp. and Skrajabinema ovis. The total number of larvae and the total number of immature and adult forms recovered from the tracers showed seasonal distributions that significantly correlated with the amount of rainfall received that month (p value ≅ 0.000 in all cases ). The species H. contortus was predominant in the herd and should be considered to be main pathogenic nematode species in these hosts under these conditions.

Minimum Setup Minimum Aberration Two‐level Split‐plot Type Designs for Physical Prototype Testing

Althoughnew technologies allow for less effortinprototyping, physical testing still remainsan importantstep in theproductdevelopment cycle. Well-planned experiments are useful to guide the decision-making process. During the design of anexperiment, one of the challenges is to balance limited resources and system constraints to obtain useful information. It iscommon that prototypes arecomposed of several parts,with some parts moredifficultto assemble thanothers. And, usually,there is only one piece available of each part type and a large number of different setups. Under these conditions, designswith randomization restrictions become attractive approaches. Considering this scenario, a new and additional criterion,minimum setup, to construct split-plot type designs is presented. Designs with the minimum number of setups of the moredifficult parts, which are especially useful for screening purposes in physical prototype testing, are discussed. The use of theproposed criterion combined with minimum aberration for selecting a regular design is shown through a real application intesting car prototypes. As a tool to practitioners, catalogs of selected 32-run minimum setup minimum aberration split-split-plot and split-split-split-plot designs are presented. More complete catalogs are available as Supporting information.Copyright

Not all Models are Polynomials

Data analysis is ultimately about making sense of a set of data—to discover systematic patterns that help predict, or nearly so, future outcomes. In the context of factorial experiments, most statistical textbooks give the impression that we must analyze the data with the aid of a factorial model. However, this is an unnecessarily dogmatic position. Mother nature is not obliged to behave factorially! A factorial model is not always the best way to summarize the result of an experiment. We demonstrate in this column, with an example from Brownlee (Brownlee, K. A. (1953). Industrial Experimentation. New York: Chemical Publishing Co. Inc.), that there are situations where a factorial polynomial model is not the best way to summarize the result of an experiment. This example also is an illustration of the power of data transformations.

Analysis of Augmented Unreplicated Factorial Designs Repeated in Time

Unreplicated designs are fairly common in industrial applications; however, there is resistance to their use in agricultural science. In the agriculture community, there is still a belief that lack of replication may prevent the experimenter from getting useful conclusions. Nevertheless, sound statistical methods that permit valid comparisons in unreplicated studies are available for many types of designs. The objective of this paper is to present an analysis procedure for unreplicated designs combining typical characteristics found in industrial experimentation (factorial designs augmented with center points) and in agricultural applications (inclusion of control treatments and repeated measurements). We illustrate the method through a real experiment to evaluate the use of sugarcane by-products in chicken diet. Specifically, it is an unreplicated two-level factorial design with two additional runs (a center point and a control treatment), with experimental units measured in two periods of time. Replication was initially planned in the case study, but the actual treatment application led to an unreplicated design. The application of the proposed method allows interpretation of the data collected. We conclude that the appropriate use of unreplicated designs in agricultural and biological research may reduce overall costs and lessen the use of in vivo testing. Copyright

Analysis of Usability and Information Architecture of the UFRN Institutional Repository

In order to identify the possible problems of usability and information architecture of the institutional repositories, the case study of the Institutional Repository of the Federal University of Rio Grande do Norte was chosen. As research hypothesis, it was established that the information architecture of the UFRN Institutional Repository interface, version 1.8.1, disadvantage usability in performing the tasks by system user groups. Data collection was carried out by applying the techniques of Cooperative Evaluation and Usability Testing of the UFRN/IR system. Problems of usability and information architecture were found in the Institutional Repository from the results obtained. The redesign of the UFRN Institutional Repository interface on areas related to the tasks presented in the research, and considering the aspects of usability and information architecture, mentioned above, we will contribute to access and visibility of information improvement.

Emotion, Affectivity and Usability in Interface Design

The intent of this paper is to provide an overview of the influence of emotion, affection and feelings during the contact between users and interfaces. Definitions of each of the aspects and relations established between them, and perceived usability and user satisfaction are presented. It was concluded that the process of interface design should include analyzes of the context, objectives and specific features and requirements.

Mixed two- and four-level experimental designs for interchangeable parts with different degrees of assembly difficulty

Purpose The purpose of this paper is to show how to properly use the method of replacement to construct mixed two- and four-level minimum setup split-plot type designs to accommodate the presence of hard-to-assemble parts. Design/methodology/approach Split-plot type designs are economical approaches in industrial experimentation. These types of designs are particularly useful for situations involving interchangeable parts with different degrees of assembly difficulties. Methodologies for designing and analyzing such experiments have advanced lately, especially for two-level designs. Practical needs may require the inclusion of factors with more than two levels. Here, the authors consider an experiment to improve the performance of a Baja car including two- and four-level factors. Findings The authors find that the direct use of the existing minimum setup maximum aberration (MSMA) catalogs for two-level split-plot type designs may lead to inappropriate designs (e.g. low resolution). The existing method of replacement for searching exclusive sets of the form (α, β, αβ) available in the literature is suitable for completely randomized designs, but it may not provide efficient plans for designs with restricted randomization. Originality/value The authors provide a general framework for the practitioners and have extended the algorithm to find out the number of generators and the number of base factor at each stratum, which guide the selection of mixed two-level and four-level MSMA split-plot type designs.

Assessing the Cooperation Portal’s Usability Based on the Proposition of Users’ Needs

This research is about identifying the Cooperation Portal users’ needs for information. The Cooperation Portal was created and implemented by the Superintendence of Informatics of the Federal University of Rio Grande do Norte (UFRN) aiming to propose a collaborative environment that would facilitate the process of transferring UFRN’s Integrated Management Systems (SIG-UFRN), which is done through cooperation agreements that are signed by federal educational institutions (IFES network) and the direct administration (CYCLE network). It is a qualitative and quantitative case study performed using log analysis and application of a questionnaire to members of the IFES and CYCLE networks. As a result, it was identified that although the interfaces are simple and well structured, with menus, self-explanatory images and search systems that help find information, the users’ real needs are not met, causing dissatisfaction when using the tool.