Balanced Block Designs Research Articles

Robustness of General Efficiency Balanced Block Designs against Missing Observations

In the present communication, some results on robustness of generalized efficiency balanced (GEB) block designs with equal block sizes (binary and non-binary) are presented. The necessary & sufficient conditions are obtained for robustness as per criteria 1 (Ghosh, 1982) when the missing observations appear in the following patterns: (i) t (≥1) observations of a design pertaining to the same treatment are missing and (ii) all observations in a block are missing but the residual design still becomes connected. Sufficient conditions for robustness according to Criteria 1 are examined in each type of GEB designs. Another criterion (Criteria 2) for robustness of a block design is the small amount loss of efficiency values of the residual design after deletion of t (≥1) observations. The declining trend of efficiency values after deletion of treatments one by one are presented graphically for measuring the robustness of designs under study.

What attributes of digital devices are important to clinicians in rehabilitation? A cross-cultural best-worst scaling study

BackgroundDigital interventions are becoming increasingly popular in rehabilitation. Understanding of device features which impact clinician adoption and satisfaction is limited. Research in the field should be conducted across diverse settings to ensure digital interventions do not exacerbate healthcare inequities. ObjectiveThis study aimed to understand rehabilitation clinicians’ preferences regarding device attributes and included a cross-cultural comparison. Materials and MethodsChoice experiment methodology (best-worst scaling) was used to survey rehabilitation clinicians across Australia and Brazil. Participants completed 10 best-worst questions, choosing the most and least important device attributes from subsets of 31 attributes in a partially balanced block design. Results were analysed using multinomial models by country and latent class. Attribute preference scores (PS) were scaled to 0–100 (least to most important). ResultsA total of 122 clinicians from Brazil and 104 clinicians from Australia completed the survey. Most respondents were physiotherapists (83%) working with neurological populations (51%) in the private/self-employed sector (51%) who had experience using rehabilitation devices (87%). Despite preference heterogeneity across country and work sector (public/not-for-profit versus private/self-employed/other), clinicians consistently prioritised patient outcomes (PS 100.0, 95%CI: 86.2–100.0), patient engagement (PS 93.9, 95%CI: 80.6–94.2), usability (PS 81.3, 95%CI: 68.8–82.5), research evidence (PS 80.4, 95%CI: 68.1–81.7) and risk (PS 75.7, 95%CI: 63.8–77.3). In Australia, clinicians favoured device attributes which facilitate increased therapy dosage (PS 79.2, 95%CI: 62.6–81.1) and encourage patient independent practice (PS 66.8, 95%CI: 52.0–69.2). In Brazil, clinicians preferred attributes enabling device use for providing clinical data (PS 67.6, 95%CI: 51.8–70.9) and conducting clinical assessments (PS 65.6, 95%CI: 50.2–68.8). ConclusionClinicians prioritise patients’ needs and practical application over technical aspects of digital rehabilitation devices. Contextual factors shape clinician preferences rather than individual clinician characteristics. Future device design and research should consider preferences and influences, involving diverse stakeholders to account for context-driven variations across cultures and healthcare settings.

OP24 Preferences Of Depressed And Depression-Prone Groups With Regard To Antidepressants In China: A Best-Worst Scaling Survey

IntroductionAntidepressants are one of the main treatment approaches for depression, and previous evidence suggests that consideration of patient preferences can improve their adherence to medication regimens. The objective was, therefore, to evaluate the preferences of depressed and depression-prone groups in China with respect to antidepressant medications.MethodsAn online survey with best-worst scaling choices was administered in depressed and depression-prone patients. The balanced independent block design generated 13 choice task profiles for each participant to answer, with each choice set consisting of four alternatives out of 13 antidepressant-specific attributes. Count analysis and a conditional logit model were used to estimate the relative importance of the 13 attributes and preference heterogeneity.ResultsThe analytical sample included 210 participants, comprising 49 individuals who had previous experience with depression and 161 who were depression prone. Participants in both groups preferred medications with a low risk of liver or kidney damage, headache or dizziness, and recurrence. There were significant differences in both groups regarding out-of-pocket costs and duration of medication. The K-means clustering further proved preference heterogeneity among the patients.ConclusionsOur study revealed patient preferences for antidepressant medication choices in China. Healthcare decision makers should consider and discuss patient preferences in the treatment decision-making process to improve patient adherence to and satisfaction with medications, and to ultimately improve patient outcomes.

Effectiveness and safety of intermittent preventive treatment with dihydroartemisinin–piperaquine or artesunate–amodiaquine for reducing malaria and related morbidities in schoolchildren in Tanzania: a randomised controlled trial

In high transmission settings, most school-aged children harbour malaria parasites without showing symptoms, often leading to anaemia and possibly impaired psychomotor and cognitive abilities. We aimed to assess the effectiveness and safety of intermittent preventive treatment for malaria in school-aged children (IPTsc) living in highly endemic areas. We did an open-label randomised controlled trial in seven primary schools in northeastern Tanzania. Schoolchildren aged 5-15 years were individually randomly assigned (1:1:1) to receive dihydroartemisinin-piperaquine, artesunate-amodiaquine, or standard of care (control) using a balanced block design. Drugs were administered by schoolteachers, with supervision from study nurses, at months 0 (baseline), 4, and 8, and were given in line with manufacturer's recommendations with dose based on the child's bodyweight. The primary endpoints were change from baseline in mean haemoglobin concentration at months 12 and 20, and clinical incidence of malaria and prevalence of parasitaemia at months 12 and 20 in the intervention groups versus the control group. The outcome data were collected through longitudinal surveys conducted every 4 months. Data were analysed on the basis of intention to treat (including all randomised participants) and per protocol (comprising children who completed the full 3-day regimen of all three IPTsc treatment rounds as assigned). This study is registered with ClinicalTrials.gov (NCT03640403). Of the 1797 children scheduled for clinical screening, 1566 were enrolled and randomly allocated (526 to receive dihydroartemisinin-piperaquine, 527 to receive artesunate-amodiaquine, and 513 to receive standard of care). Due to COVID-19-related school closures, only two schools were visited at month 12 (135 children in the dihydroartemisinin-piperaquine group, 131 in the artesunate-amodiaquine group, and 118 in the control group). At month 12, compared with the control group, the change from baseline in mean haemoglobin concentration was increased by 0·5 g/dL (95% CI 0·2 to 0·8; p<0·0001) in the dihydroartemisinin-piperaquine group and 0·5 g/dL (0·2 to 0·7; p=0·0020) in the artesunate-amodiaquine group in the intention-to-treat analysis (with similar findings in the per protocol analysis). In the same period, in the intention-to-treat analysis, the prevalence of malaria parasitaemia increased from 28·5% (138 of 485 participants) to 33·6% (39 of 116) in the control group, but decreased from 28·0% (139 of 497) to 12·0% (15 of 125) in the dihydroartemisinin-piperaquine group (-21·6 percentage points [95% CI -31·9 to -11·3], p=0·0001 vs control at month 12) and from 24·7% (124 of 502) to 16·0% (20 of 125) in the artesunate-amodiaquine group (-17·6 percentage points [-28·4 to -6·9], p=0·0015). The decrease for artesunate-amodiaquine was larger in the per protocol analysis (-25·3 percentage points [-36·3 to -14·2], p<0·0001). The protective effect of IPTsc against malaria parasitaemia was 64% (95% CI 39 to 79; p<0·0001) for dihydroartemisinin-piperaquine and 52% (23 to 70; p=0·0015) for artesunate-amodiaquine in the intention-to-treat analysis, and was slightly higher on per protocol analysis. The protective effect against clinical malaria at month 12 was 20% (95% CI 9 to 29; p=0·0002) for dihydroartemisinin-piperaquine and 19% (8 to 28; p=0·0004) for artesunate-amodiaquine. No significant differences in any primary outcomes between the intervention and control groups were noted at month 20. Dihydroartemisinin-piperaquine and artesunate-amodiaquine were associated with a small number of mild adverse events, and there were no treatment-related serious adverse events or deaths. IPTsc with dihydroartemisinin-piperaquine or artesunate-amodiaquine is a safe and effective approach to reducing malaria parasitaemia, clinical malaria, and related morbidities, and is feasible to implement through programmes delivered by schoolteachers. Flemish Interuniversity Council (VLIRUOS), EU EDCTP2 programme (MaReCa project), and Global Minds 2019. For the Swahili translation of the abstract see Supplementary Materials section.

Some constructions of nested balanced equireplicate block designs

Some constructions of nested balanced equireplicate block designs

The use of dimensional analysis for modeling tractor fuel consumption for harrowing operation

Fuel consumption model for predicting tractor fuel consumption per working area for harrowing operation has been developed using dimensional analysis. Generalized reduced gradient method of Excel solver was adopted for the establishment of the model’s constant. The model was validated by simulating the experimental results into the equation and coefficient determination (r2). Graphical comparison, root mean square error, and paired t-test were also use to validate. The field experiment was carried out at Rivers Institute of Agricultural Research and Training Farm in Rivers State University, Port Harcourt. The group balanced block design was adopted. The design consisted of 9 experimental treatments with three replicates. The experimental fuel consumption per working area was determined by quantity of fuel used per working area with the aid of fuel flow meter. The field test parameters were measured accordingly with their specific standard procedures. The field test parameters including bulk density, tractor forward speed, harrowing depth, and cone index were simulated with fuel consumption to obtain the constants in the prediction model. The developed model showed good agreement between measured and predicted results with high coefficient of determination and low root mean square error. The paired t-test results showed no significant difference at 95 and 99 % confidence levels. Thus, suggested that the model could be used for predicting tractor fuel consumption for harrowing operation.

Graph decomposition methods for variance balanced block designs with correlated errors

Block designs have an important historical footing in the design of experiments. Let θ be the treatment mean vector in the statistical model with fixed block effects. It is desirable to have the covariance of the least squares estimator of the treatment effects, Cov(θ̂), be a completely symmetric matrix. When this occurs, we have a variance balanced design (VBD). It is known that a pairwise balanced design can be converted into a VBD by choosing blocks with a multiplicity inversely proportional to the block size. This assumes that experimental errors are uncorrelated. However, this need not be the case, especially in ecological experiments where blocks have spatial correlation or laboratory settings with temporal correlation. This paper proposes the use of graph decompositions as a generalization of balanced incomplete block designs for the construction of VBDs in the presence of correlated errors. A general result is obtained to construct VBDs for various error correlation structures. Several applications are given to illustrate the relationship between graph decompositions and VBDs.

Universally optimal balanced block designs for interference model

Universally optimal balanced block designs for interference model

Evidence factors from multiple, possibly invalid, instrumental variables

Valid instrumental variables enable treatment effect inference even when selection into treatment is biased by unobserved confounders. When multiple candidate instruments are available, but some of them are possibly invalid, the previously proposed reinforced design enables one or more nearly independent valid analyses that depend on very different assumptions. That is, we can perform evidence factor analysis. However, the validity of the reinforced design depends crucially on the order in which multiple instrumental variable analyses are conducted. Motivated by the orthogonality of balanced factorial designs, we propose a balanced block design to offset the possible violation of the exclusion restriction by balancing the instruments against each other in the design, and demonstrate its utility for constructing approximate evidence factors under multiple analysis strategies free of the order imposition. We also propose a novel stratification method using multiple, nested candidate instruments, in which case the balanced block design is not applicable. We apply our proposed methods to evaluate (a) the effect of education on future earnings using instrumental variables arising from the disruption of education during World War II via the balanced block design, and (b) the causal effect of malaria on stunting among children in Western Kenya using three nested instruments.

Investigating Medical Student's Preferences for Internet-Based Healthcare Services: A Best-Worst Scaling Survey.

Objective: This study aimed to investigate the importance of providing Internet-based healthcare services based on the preference of a sample of medical students in China.Methods: An online best-worst scaling (BWS) survey with Case 1 design was conducted. Balanced independent block design generated 12 choice task profiles for each participant to answer. Descriptive analysis was used to describe the respondents' characteristics; Multinomial and mixed logit regression methods were used to investigate the importance of Internet-based services based on respondents' preferences.Results: A total of 1,296 students completed the online survey and rated “Clinical Service,” “Decision Aids,” and “Public health” as the three most important services that should be provided through an Internet-based healthcare system. Providing “Medical Education” via the Internet was chosen as the least important service by the respondents. Subgroup analysis indicated that students studying clinical medicine and non-clinical medicine considered providing “Medical Education” and “Public Health,” respectively, as more important services than others.Conclusions: This BWS study demonstrated that providing “Clinical Service,” “Decision Aids,” and “Public Health” through the Internet are the three most important services based on medical students' preferences in China. Further research is needed to investigate how to improve medical students' skills in using internet-based healthcare services in medical education programs.

Breeding for higher yield, early maturity, wider adaptability and waterlogging tolerance in soybean (Glycine max L.): A case study

Breeding for higher yield and wider adaptability are major objectives of soybean crop improvement. In the present study, 68 advanced breeding lines along with seven best checks were evaluated for yield and attributing traits by following group balanced block design. Three blocks were constituted based on the maturity duration of the breeding lines. High genetic variability for the twelve quantitative traits was found within and across the three blocks. Several genotypes were found to outperform check varieties for yield and attributing traits. During the same crop season, one of the promising entries, NRC 128,was evaluated across seven locations for its wider adaptability and it has shown stable performance in Northern plain Zone with > 20% higher yield superiority over best check PS 1347. However, it produced 9.8% yield superiority over best check in Eastern Zone. Screening for waterlogging tolerance under artificial conditions revealed that NRC 128 was on par with the tolerant variety JS 97–52. Based on the yield superiority, wider adaptability and waterlogging tolerance, NRC 128 was released and notified by Central Varietal Release Committee (CVRC) of India, for its cultivation across Eastern and Northern Plain Zones of India.

Comparison of MRI appendix biometrics in children with and without acute appendicitis.

The goal of this study is to improve MRI-specific diagnostic criteria for pediatric appendicitis through comparison of normal and abnormal appendix-related imaging features. A retrospective multireader-multicase design was used, including non-contrast MRI performed for suspected pediatric appendicitis following non-diagnostic US from January 2014 to December 2017. Positive diagnosis was defined by surgical pathology or symptom resolution after antibiotics. Four pediatric radiologists independently graded study biometrics while blinded to clinical data. Balanced complete block design was used to determine performance characteristics. Global diagnosis of appendicitis (208 studies) had sensitivity 90.6% and specificity 97.7%. Median appendix diameter was 10.4mm among positive cases and 5.8mm among negative cases (p < 0.001) with an optimal diagnostic cutoff of 7.5mm (sensitivity 89.4%, specificity 86.5%). Median appendix wall thickness was 2.6mm among positive cases and 1.7mm among negative cases (p < 0.001) with an optimal diagnostic cutoff of 2.3mm (sensitivity 63.1%, specificity 82.9%). Performance characteristics for qualitative appendix features included distinguishable appendix luminal signal (sensitivity 89.6%, specificity 83.7%), intraluminal fluid-signal intensity (sensitivity 63.6%; specificity 52.3%), intraluminal signal intermediate between fluid and bowel wall (sensitivity 91.0%; specificity 37.1%), appendicolith (sensitivity 34.9%; specificity 100.0%), intraluminal layering (sensitivity 25.9%; specificity 100.0%), hyperintense appendix wall signal (sensitivity 31.7%; specificity 100.0%), periappendiceal fluid (sensitivity 66.8%; specificity 72.5%), periappendiceal fatty edema (sensitivity 91.3%; specificity 94.5%), and free pelvic fluid (sensitivity 88.5%; specificity 26.0). This study provides MRI-specific performance of pediatric appendicitis quantitative and qualitative biometrics with peri-appendiceal fatty edema, appendix diameter > 7.5mm, and distinguishable appendix luminal signal demonstrating the highest overall accuracy. • This retrospective multireader-multicase study characterized magnetic resonance imaging-specific diagnostic accuracy of quantitative and qualitative biometrics for pediatric appendicitis. • The optimal quantitative diagnostic thresholds for an abnormal pediatric appendix at MRI included diameter and wall thickness of 7.5mm and 2.3mm, respectively. • Qualitative imaging biometrics with high specificity for pediatric appendicitis on MRI included the presence of distinguishable appendix lumen signal from wall signal, appendicolith, intraluminal fluid-fluid layer, appendix wall hyperintensity, and peri-appendiceal fatty edema.

New Results Regarding the Construction Method for D‑optimal Chemical Balance Weighing Designs

We study an experiment in which we determine unknown measurements of p objects in n weighing operations according to the model of the chemical balance weighing design. We determine a design which is D‑optimal. For the construction of the D‑optimal design, we use the incidence matrices of balance incomplete block designs, balanced bipartite weighing designs and ternary balanced block designs. We give some optimality conditions determining the relationships between the parameters of a D‑optimal design and we present a series of parameters of such designs. Based on these parameters, we will be able to set down D‑optimal designs in classes in which it was impossible so far.

The Interplay Between Block Design Theory and Channel Estimation in Visible Light System

The problem of channel gain estimation in visible light communications and positioning is considered in this article. Pilot sequences are designed for simultaneously estimating the channel gains of multiple transmitters in a light system and satisfying the average and maximum transmit power constraint due to illumination purpose. This article illustrates how to design the optimal pilot sequences that minimise the noise variance experienced by a receiver although the optimisation problem is non-convex. Lower bounds on the noise variance are derived for systems with ambient light and systems without ambient light. These bounds reveal the relationship between noise variance, the average transmit power, the maximum transmit power, the number of light sources and pilot length. The necessary and sufficient conditions for the bounds to hold with equality are derived. These conditions establish a bridge between block design theory and channel estimation in visible light systems. Optimal pilot designs which achieve the lower bounds on noise variance can be obtained from balanced block designs and pairwise balanced designs. This article also shows how to optimise the average transmit power of a pilot design for minimising noise variance.

Optimal balanced block designs for correlated observations

The construction of universally optimal designs, if such exist, is difficult to obtain, especially when there are some nuisance effects or correlated errors. The hub correlation is a special correlation structure with applications to experiments in genetics, networks and other areas in industry and agriculture. There may be restrictions on the correlation values of the hub structure depending on the experiment. Optimality of block designs under hub correlation has been studied for the case of a constant correlation value. In this article, we consider the hub structure when one of the correlation values is different from the others, and the universally optimal block designs, binary or non‐binary, are theoretically obtained. Also, we introduce an algorithm to construct the optimal designs. The Canadian Journal of Statistics 48: 596–604; 2020 © 2020 Statistical Society of Canada

Nearest neighbor balanced block designs for autoregressive errors

In this paper we study the problem of finding neighbor optimal designs for a general correlation structure. We give universal optimality conditions for nearest-neighbor (NN) balanced block designs when observations on the same block are modeled by an autoregressive AR(m) process with arbitrary order m. The cases \(m=1,2\) have been studied by Grondona and Cressie (Sankhyā Indian J Stat Ser A 55(2):267–284, 1993) for AR(2) and by Gill and Shukla (Biometrika 72(3):539–544, 1985a, Commun Stat Theory Methods 14(9):2181–2197, 1985b) and Kunert (Biometrika 74(4):717–724, 1987) for AR(1); we extend these results to the cases \(m \ge 3\).

Effectiveness and safety of intermittent preventive treatment for malaria using either dihydroartemisinin-piperaquine or artesunate-amodiaquine in reducing malaria related morbidities and improving cognitive ability in school-aged children in Tanzania: A study protocol for a controlled randomised trial

BackgroundIn high transmission settings, up to 70% of school-aged children harbour malaria parasites without showing any clinical symptoms. Thus, epidemiologically, school aged children act as a substantial reservoir for malaria transmission. Asymptomatic Plasmodium infections induce inflammation leading to iron deficiency anaemia. Consequently, anaemia retards child growth, predisposes children to other diseases and reduces cognitive potential that could lead to poor academic performance. School aged children become increasingly more vulnerable as compared to those aged less than five years due to delayed acquisition of protective immunity. None of the existing Intermittent Preventive Treatment (IPT) strategies is targeting school-aged children. Here, we describe the study protocol of a clinical trial conducted in north-eastern Tanzania to expand the IPT by assessing the effectiveness and safety of two antimalarial drugs, Dihydroartemisinin-Piperaquine (DP) and Artesunate-Amodiaquine (ASAQ) in preventing malaria related morbidities in school-aged children (IPTsc) living in a high endemic area. Methods/designThe trial is a phase IIIb, individual randomized, open label, controlled trial enrolling school children aged 5–15 years, who receive either DP or ASAQ or control (no drug), using a “balanced block design” with the “standard of care” arm as reference. The interventional treatments are given three times a year for the first year. A second non-interventional year will assess possible rebound effects. Sample size was estimated to 1602 school children (534 per group) from selected primary schools in an area with high malaria endemicity. Thick and thin blood smears (to measure malaria parasitaemia using microscope) were obtained prior to treatment at baseline, and will be obtained again at month 12 and 20 from all participants. Haemoglobin concentration using a haemoglobinometer (HemoCue AB, Sweden) will be measured four monthly. Finger-prick blood (dried bloodspot-DBS) prepared on Whatman 3 M filter paper, will be used for sub-microscopic malaria parasite detection usingPCR, detect markers of drug resistance (using next generation sequencing (NGS) technology), and malaria serological assays (using enzyme-linked immunosorbent assay, ELISA). To determine the benefit of IPTsc on cognitive and psychomotor ability test of everyday attention for children (TEA-Ch) and a ‘20 m Shuttle run’ respectively, will be conducted at baseline, month 12 and 20. The primary endpoints are change in mean haemoglobin from baseline concentration and reduction in clinical malaria incidence at month 12 and 20 of follow up. Mixed design methods are used to assess the acceptability, cost-effectiveness and feasibility of IPTsc as part of a more comprehensive school children health package. Statistical analysis will be in the form of multilevel modelling, owing to repeated measurements and clustering effect of participants. DiscussionMalaria intervention using IPTsc strategy may be integrated in the existing national school health programme. However, there is limited systematic evidence to assess the effectiveness and operational feasibility of this approach. School-aged children are easily accessible in most endemic malaria settings. The evidence from this study will guide the implementation of the strategy to provide complementary approach to reduce malaria related morbidity, anaemia and contribute to the overall burden reduction. Trial registrationClinicaltrials.gov: NCT03640403, registered on Aug 21, 2018, prospectively registered.Url https://www.clinicaltrials.gov/ct2/show/NCT03640403?term=NCT03640403&rank=1.

Efficiency balanced designs for bootstrap simulations

This paper considers the balanced resampling design approach of generating bootstrap samples to handle the simulation error problem in bootstrap estimation of mean and variance of a sample statistic of interest. A class of balanced n-arry block design, slightly different from the definition of Tocher (1952), is defined and its necessary conditions for the existence of these designs are derived. In particular, an infinite series of balanced n-arry block designs are found to be efficiency balanced, i.e., every contrast of element (observation) totals has the same loss of information. As an application in bootstrap method, the eccentric class of efficiency balanced n-arry block design (termed Efficient Bootstrap Sample Design (EBSD(n)) can be used to generate resamples of sample size n to achieve an exact bootstrap estimation of mean and variance of statistic “sample average”, i.e., a collection of bootstrap data samples and corresponding bootstrap sample averages where mean and variance of this empirical collection of sample averages match the first two theoretical central moments i.e., moments about the sample average. The EBSD(n) solely depends on the existence of balanced incomplete block design B[ 4n-2, 2n-1, n, n-1] for n ≥ 2. Thus the implementation of computer algorithm for spawning bootstrap samples using EBSD(n) is simple and straightforward for recapitulating sampling characteristics such as standard error of predefined computable symmetric and non symmetric sample statistic of interest.

Optimal partial triallel cross designs through diallel cross designs

Das and Gupta constructed optimal block designs for triallel crosses through Nested balanced block designs. In the present paper we are constructing three series of optimal partial triallel cross designs through complete diallel cross designs which have been obtained by nested balanced incomplete block designs.

Remarks about a construction method for D-optimal chemical balance weighing designs

Summary This paper presents some constructions of regular D-optimal weighing designs based on the incidence matrices of a balanced incomplete block design, balanced bipartite weighing design and ternary balanced block design. We determine optimality conditions and relations between the parameters of the design, and give an example.