Balanced Block Designs Research Articles

On the construction and existence of a certain class of complete diallel cross designs

In this paper the construction and existence of complete diallel cross designs as nested balanced incomplete block (BIB) designs with sub-block size two are discussed. Two simple and general methods of constructing these designs using binary pairwise balanced designs and strongly equineighboured designs are given. Also, the necessary conditions for the existence of nested BIB designs with sub-block size two and super-block size four are found to be sufficient.

Answer to the comments of K. Dobbin, J. Shih and R. Simon on the paper 'Evaluation of the gene-specific dye-bias in cDNA microarray experiments'

We would like to thank K. Dobbin, J. Shih and R. Simon for their comments about Martin-Magniette et al. (2005). Their remarks relate to the design of microarray experiments and notably about the use of dye-swaps. We, however, want to make it clear that our manuscript primarily focuses on the detection, quantification and correction of the gene-specific dye-bias introduced in dual-color microarray experiments. The most important point in Martin-Magniette et al. (2005) is the following: by dint of studying technical errors, we will be able to identify and then to remove most of them. For the first time, in Martin-Magniette et al. (2005), we were able to quantify the genespecific dye bias by calculating the Labelling Bias Index, (LBI). The LBI measured on different array types shows that this artifact seems to be very low in some cases and could be thus neglected. However, it is high in other cases and it cannot thus be neglected for data issued from these array types. This measure is of crucial importance as it allows users to evaluate the impact of this bias on their data. Moreover, we think that each platform should at least know in what class it belongs for each array types. Although this artifact is not lowered nor understood, it is simply dangerous to underestimate it. The gene-specific dye bias is not an inevitability and can be well controlled, as we point out in our paper. Recently, in another paper, Dobbin et al. (2005) studied the genespecific dye bias. Although they reached the same conclusions, some of their remarks are explained in Martin-Magniette et al. (2005): e.g. Dobbin et al. (2005) have found that ‘(the gene-specific) dye bias appears to have masked the true differential expression’. This is explained in Martin-Magniette et al. (2005): the variance associated to a gene is overestimated by the dye bias effect in model (2) of Martin-Magniette et al. Dye-swaps constitute a simple and effective design to remove gene-specific dye bias when it is high. Nevertheless, we agree with Dobbin et al. (2005), that a balanced block design may be better than dye-swaps in some situations. As the former designs allow the use of more biological samples, the estimation of the biological variability will be more precise. Even if balanced block designs are statistically more efficient, the following considerations should be taken into account before choosing the experimental design:

An extension of the Williams trend test to general unbalanced linear models

The trend test of Williams is one of the most common approaches to test for monotone dose-response relationships. It has originally been introduced for one-way layouts. Applications of the Williams test beyond balanced block designs have not been described yet, what severely restricts its use in practice. An extension of Williams’ test to general unbalanced linear models is presented which allows the inclusion of covariates and/or factorial treatment structures. The test statistic of Williams is rewritten as the maximum of a finite number of standardized linear combinations of the means. The associated distribution function is seen to be available in closed form. Accordingly, p -values/critical values and power/sample sizes can be computed thoroughly. The methods are also applied to a modified version of Williams’ test. Data examples and numerical comparisons suggest a good performance of both extended approaches when compared to current competing methods.

Randomized Controlled Trial of Olanzapine in the Treatment of Cognitions in Anorexia Nervosa

Recovery from anorexia nervosa is confounded by intrusive anorectic cognitions and rituals. It has been observed that olanzapine, an atypical antipsychotic, can reduce this anorexic rumination. A pilot study was designed to test the effectiveness of olanzapine in this role. A randomized trial of olanzapine versus chlorpromazine, with anorexic rumination as the primary outcome, was conducted. Of the 26 patients who presented, 15 were randomized in a balanced block design, eight to olanzapine and seven to chlorpromazine. Only the olanzapine group had a significant reduction in the degree of rumination. Olanzapine may be of benefit in anorexia nervosa by causing a reduction in anorexic rumination.

Optimum chemical balance weighing design with diagonal matrix of errors based on balanced block designs

The paper is studying the estimation problem of individual weights of objects using the chemical balance weighing design under the restriction on the number of times in which each object is weighed. Additionally, we assume that the errors are uncorrelated and they have different variances. There are given the lower bound of the variance of each of the estimated weights and the sufficient and necessary conditions under which this lower bound is attained. For the new construction method for optimum chemical balance weighing designs, we use the incidence matrices of the balanced incomplete block designs and the balanced bipartite weighing designs.

Evaluation of an automated test ordering and feedback system for general practitioners in daily practice

Objective: To evaluate the use of an automated test ordering and feedback system (named GRIF) in daily practice. The system produces recommendations to general practitioners (GPs) to improve the application of accepted practice guidelines for test ordering. Methods: A randomised controlled trial with balanced block design was carried out in general practices in two regions of the Netherlands from August 2000 to July 2001. We implemented the GRIF system on the workstations at the offices of the participating GPs. The GPs ( n = 11) were asked to use GRIF during patient consultation instead of filling in the paper request form. The system displayed critical comments about their non-adherence to the guidelines as apparent from the request forms. Results: The median time of producing the comments plus the response time of the GP was 13 s. Of the 2780 presented recommendations, 4.3% were accepted. Advice of the GRIF system that presents a concrete test to request in a particular situation is adhered to most frequently. Finally, there seems to be a decrease of accepted comments over the trial period. Conclusion: Computerised recommendations should contain, if possible, suggestions for alternative tests to improve the application of these recommendations. Furthermore, creative solutions must be developed to avoid that GPs get used to the recommendations of critiquing systems and to stimulate a better adherence to these recommendations.

Structurally Incomplete Row–Column Designs

This article studies the optimality and construction aspects of structurally incomplete row–column designs in which the number of non-empty nodes in rows and/or columns are unequal. Universal optimality of structurally incomplete row-column designs with unequal row and/or column sizes has been investigated. General methods of construction of universally optimal designs are obtained using pairwise balanced block designs and block designs with nested rows and columns. One method of construction gives SIRC design with equal row and equal column sizes. A method of construction of structurally incomplete row–column designs for comparing test treatments with control treatment(s) is also given.

Robustness of complete diallel crossing plans against exchange of one cross

The robustness aspects of block designs for complete diallel crossing plans against the exchange of one cross using connectedness and efficiency criteria have been investigated. The exchanged cross may have either no line in common or one line in common with the original cross. It has been found that randomized complete block (RCB) designs for complete diallel crosses and binary balanced block designs for complete diallel crosses are robust against the exchange of one cross in one observation. The RCB designs for diallel crosses have been shown to be robust against the exchange of one cross with another cross in all the blocks. The non-binary balanced block designs obtainable from Family 5 of Das et al. (1998) have also been found to be robust against the exchange of one cross.

Optimality of neighbor balanced designs under mixed effects model

This paper generalizes Druilhet's results on optimality of circular neighbor balanced block designs under the model with fixed neighbor effects. It is shown that some of these designs are also optimal under the model with random neighbor effects.

Optimal and efficient repeated measurements designs for comparing test treatments with a control

Rearranging the sequence of test treatments and control treatment within each block of an A-optimal balanced treatment block design such that certain conditions are satisfied, the resulting design is an A-optimal repeated measurements designs when blocks are regarded as units or periods. The efficiencies of designs which are obtained from universally optimal repeated mea-surements designs with test treatments only by changing some treatment labels into control treatment are given.

Contrast adaptation: paradoxical effects when the temporal frequencies of adaptation and test differ.

Previous studies of human contrast adaptation employing visually evoked potentials (VEP) have revealed contradictory results, namely, either a reduction or an enhancement in VEP amplitude. In a cross-adaptation experiment, we explored the possibility that differences in the temporal frequency of adapting and test patterns played a role. Phase-reversing checkerboard stimuli [1-deg check size, temporal frequency 8.5 or 17 reversals per second (rps)] served as adaptation and test pattern with contrasts of 0 or 97%. In 13 subjects, we recorded both retinal (PERG) and cortical (VEP) steady-state responses simultaneously. In a balanced block design, all four combinations of the temporal adaptation and test frequencies were employed. Contrast adaptation reduced the PERG amplitude by about 20% in every temporal condition (P < 0.001). The VEP amplitude was strongly affected by adaptation, but the effect differed in magnitude and sign depending on condition: With identical adaptation and test frequency, amplitude was reduced by 15% (P = 0.07) at 8.5 rps and by 38% at 17 rps (P < 0.05). Adapting at 8.5 rps and testing at 17 rps had a tiny (14%) insignificant effect, whereas adapting at 17 rps and testing at 8.5 rps revealed an amplitude enhancement of 27% (P < 0.05). These strong temporal cross-adaptation effects (in the VEP, but not in the PERG) suggest that the adaptable cortical mechanisms (gain control) can be narrowly tuned in their temporal properties. A sizable adaptation effect can even change its sign when varying the temporal frequency by a factor of two. This finding resolves contradictions between previous VEP adaptation studies and reconciles them with psychophysical findings.

Split Block Designs

Split block designs were introduced by Ozawa et al (2000) who established the optimality of the balanced split block designs for the estimation of the interaction effect. Here, we establish the same separately for each of the four strata and under fewer restrictions on the class of competing designs. Further, we give procedures for combined estimation and illustrate these for the balanced split block designs.

Comparing more than one treatment to more than one control in incomplete blocks

Abstract The class of balanced treatment incomplete block designs is generalized to allow for comparison of v 1 test treatments and v 2 control treatments. The generalized class is equivalent to the class of balanced bipartite block designs considered by Jaggi, Gupta, and Parsad. Some results on design construction and A-optimality are given for small values of v 1 and v 2 . Algorithms are developed for computing simultaneous confidence bounds for all test treatment versus control contrasts.

Constructions for a certain type of balanced bipartite block designs

A special type of balanced bipartite block designs is defined and a lower bound of the number of superblocks of the design is given. Furthermore, some constructions are provided for the balanced bipartite block design attaining the lower bound.

A note on the relations between two ternary balanced block designs and chemical balance weighing designs

A note on the relations between two ternary balanced block designs and chemical balance weighing designs

Crescimento da cultura principal e da soca de genótipos de arroz irrigado por inundação

Com o objetivo de identificar e avaliar as características fisiológicas que se correlacionam com o rendimento de grãos da cultura principal e da soca para estabelecer critérios de seleção de genótipos de arroz irrigado por inundação com maior capacidade produtiva de grãos, foi conduzido um experimento em solo Gley Pouco Húmico. O delineamento experimental usado foi o de blocos balanceados em grupos, com quatro repetições, onde os grupos consistiram nos ciclos e, as parcelas, dos genótipos em cada ciclo. Na soca, os genótipos de ciclo médio apresentaram maiores valores de matéria seca total da parte aérea e de folha que os de ciclo curto e, na cultura principal, além desses parâmetros, foram superiores na matéria seca de raiz, densidade radicular, índice e duração de área foliar. Os valores de razão de área foliar, área foliar específica e razão de peso de folha da cultura principal foram mais elevados aos 20 dias após a emergência das plântulas e declinaram ao longo do ciclo. Foram realizadas correlações entre as variáveis estudadas e entre estas e o rendimento de grãos da cultura principal e da soca. Os índices fisiológicos da cultura principal correlacionaram-se com o rendimento de grãos, não apresentando, contudo, correlação significativa com o rendimento de grãos da soca.

Pairwise balanced designs from finite fields

Developing previous work by R.C. Bose, R.M. Wilson, M. Greig and the author, we give a general construction for difference families over finite fields. All the DFs constructed before were generated by a single initial base block so that they were uniform. Here we also consider DFs generated by two or more initial base blocks. These DFs give rise to pairwise balanced designs which of course are balanced block designs exactly when the initial base blocks have constant size.

Cultural values, media richness and telecommunication use in an organization

This paper deals with adapting the telecommunication services of an organization to the diversity of individual value orientations related to culture. After a discussion of the processes linking telecommunication use to cultural values, we show on empirical grounds the relationship between the preference of the individual for organizational cultures and his or her telecommunication use (fax, email (electronic mail), vmail (voice mail) and telephone). The cultural values were measured for 223 individuals in a French company using Q sort with balanced block design while telecommunication use was measured through a diary method. The final analysis was performed on 799 internal communications of 145 individuals having access to the four telecommunication services. In particular we found that the use of new media was more related to an orientation towards innovation or reactivity or entrepreneurship than the telephone. Email appeared as associated to relation-oriented rather than task-oriented value and suggests that the amount of feedback plays a role in the process of telecommunications media choice. We argue that cultural analysis is not only an interesting complementary approach to information richness theory for understanding telecommunication choices, but can also lead to different decisions. As an example, we examine the decision to withdraw either vmail or email in a downsizing situation.

Construction of Non-Proper Balanced Bipartite Block Designs

The purpose of this paper is to give some methods of construction of balanced bipartite block designs. These designs are useful for comparing a set of test treatments to a set of control treatments. The methods of construction of non-proper balanced bipartite block designs are based on the UBe of incidence matrices of block designs with known patterns, such as balanced incomplete block (BiB) designs, group divisible (GD) designs and variance balanced (VB) designs. Using resolvable BIB designs and certain GD designs, two methods of construction of proper balanced bipartite block designs have also been given.

Construction of nested balanced block designs, rectangular designs andq-ary codes

Construction of nested balanced incomplete block (BIB) designs, nested balanced ternary designs and rectangular designs from given nested BIB designs and resolvable BIB designs are described. New constructions ofq-ary codes from nested BIB designs and balanced bipartite weighing designs are also given.