Relevant Statistical Methods Research Articles

Environmental Correlates of Bronchial Asthma in Children in a Slum of Meerut - A Cross-Sectional Study

Introduction: In India, an estimated 57,000 deaths were attribute d to Asthma in 2004 & it was seen as one of the lea ding cause of morbidity and mortality (WHO 2004). The range of prevalence of Bronchial asthma in chil dren in India varied from 2% to 20%. So far, no community based studies have been conducted in Western Uttar Pradesh to fin d out the prevalence of bronchial asthma in children. The pre sent study is an effort in that direction. Objective : To determine the prevalence of bronchial asthma among children of 5 - 15 years and its environmental determinants. Methods : A cross sectional community based study was conducted by interviewing the parents of randomly selected childre n in the age group of 5- 15 years using International Study on A llergy And Asthma In Childhood (ISAAC) Questionnaire. Assuming the prevalence of bronchial asthma to be 10% at 95% confidence interval and allowing a relative precis ion of 20% for the estimate and expecting a non response rate of 5 %, the sample size was calculated as 907. The observat ions thus obtained were tabulated and analysed using relevant statisti cal methods. Results: A total of 880 children of 5- 15 yrs participated in the study showing a response rate of 97.02%. The prevalence of asthma was found to be 9.3%. The prevalence of asthma was found to be associated with inadequate ventilation (OR=2.71) and presence of pets (OR= 2.70 ) Conclusion: The prevalence of asthma was found to be 9.3% and it warrants a national program to reduce the morbid ity in children.

An Empirical Study on Efficient Market Hypothesis: The Case of Indian Capital Markets

The objective of this paper is to study the efficiency of Indian stock markets during the period 2001-2011. The weak form of efficient markets is extensively tested using NIFTY and 6 major NSE sectoral indices Pharma, IT, MNC, Bank, FMCG and Nifty Junior. Univariate time series analysis of indices returns is carried using tests for randomness / non-stationarity - runs test, unit root testing. ACF, correlograms and other relevant statistical methods. The study concludes that Indian markets are inefficient in its weak form for the study period.

Statistical methods for bioimpedance analysis

Abstract This paper gives a basic overview of relevant statistical methods for the analysis of bioimpedance measurements, with an aim to answer questions such as: How do I begin with planning an experiment? How many measurements do I need to take? How do I deal with large amounts of frequency sweep data? Which statistical test should I use, and how do I validate my results? Beginning with the hypothesis and the research design, the methodological framework for making inferences based on measurements and statistical analysis is explained. This is followed by a brief discussion on correlated measurements and data reduction before an overview is given of statistical methods for comparison of groups, factor analysis, association, regression and prediction, explained in the context of bioimpedance research. The last chapter is dedicated to the validation of a new method by different measures of performance. A flowchart is presented for selection of statistical method, and a table is given for an overview of the most important terms of performance when evaluating new measurement technology.

Evaluation of Different Approaches for Confounding in Nonrandomised Observational Data: A Case-Study of Antipsychotics Treatment

Although randomised controlled trials are regarded as the gold standard for treatments efficacy, evidence from observational studies remains relevant. To address the problem of possible confounding in these studies, investigators must employ analysis methods that adjust for confounders and lead to an unbiased estimation of the treatment effect. In this paper, the authors describe two relevant statistical methods. The first method represents the classical approach consisting of a multiple regression model including the effects of treatment and covariates. This approach considers the relation between prognostic factors and the outcome variable as a relevant criterion for adjustment. The second method is based on the propensity score, and focuses on the relation between prognostic factors and treatment assignment. These approaches were applied to a cohort of 183 French schizophrenic patients who were followed for a 2-year period (from 1998 to 2000). The probability of relapse according to antipsychotic treatment exposure was modelled using Cox regression models with the two statistical methods. Goodness-of-fit criteria were used to compare the modelling approaches. This study demonstrates that the propensity score, a predicted probability, has an important balancing property that underscores its value in strengthening the results of nonrandomised observational studies.

Early Childhood Determinants of Bronchial Asthma - A Cross-Sectional Study from Western Uttar Pradesh

Background: In India, an estimated 57,000 deaths were attributed to Asthma in 2004, and it was seen as one of the leading causes of morbidity and mortality. The range of prevalence of bronchial asthma in children in India varied from 2% to 20%. There has been a constant increase in asthma prevalence worldwide in the last two decades, and the same is being observed in India. The objective was to determine the prevalence of bronchial asthma among children of 5-15 years and its early childhood risk factors in a slum of Meerut. Methods: A cross-sectional community-based study was conducted by interviewing parents of randomly selected children using the International Study on Allergy and Asthma in Childhood Questionnaire. Assuming the prevalence of bronchial asthma to be 10% at 95% confidence interval and allowing a relative precision of 20% for the estimate, the sample size was calculated as 864. The observations thus obtained were analyzed using relevant statistical methods. Results: A total of 880 children of 5-15 years participated in the study showing a response rate of 97.02%. The prevalence of asthma was found to be 9.3%. Non breast fed children and more than 3 episodes of lower respiratory tract infections in infancy were found to be associated with bronchial asthma. Conclusion: The high prevalence of bronchial asthma warrants a national program to reduce the morbidity in children.

Psychometric evaluation of ADAS-Cog and NTB for measuring drug response

To conduct a psychometric analysis to determine the adequacy of instruments that measure cognition in Alzheimer's disease trials. Both the Alzheimer's Disease Assessment Scale - Cognition (ADAS-Cog) and the Neuropsychological Test Battery (NTB) are validated outcome measures for clinical trials in Alzheimer's disease and are approved also for regulatory purposes. However, it is not clear how comparable they are in measuring cognitive function. In fact, many recent trials in Alzheimer's disease patients have failed and it has been questioned if ADAS-Cog still is a sensitive measure. The present paper examines the psychometric properties of ADAS-Cog and NTB, based on a post hoc analysis of data from a clinical trial (NCT01024660), which was conducted by AstraZeneca, in mild-to-moderate Alzheimer's disease (AD) patients, with a Mini Mental State Examination (MMSE) Total score 16-24. Acceptability, reliability, different types of validity and ability to detect change were assessed using relevant statistical methods. Total scores of both tests, as well as separate domains of both tests, including the Wechsler Memory Scale (WMS), Rey Auditory Verbal Learning Test (RAVLT) and Delis-Kaplan Executive Function System (D-KEFS) Verbal Fluency Condition, were analyzed. Overall, NTB performed well, with acceptable reliability and ability to detect change, while ADAS-Cog had insufficient psychometric properties, including ceiling effects in 8 out of a total of 11 ADAS-Cog items in mild AD patients, as well as low test-retest reliability in some of the items. Based on a direct comparison on the same patient sample, we see advantages of the NTB compared with the ADAS-Cog for the evaluation of cognitive function in the population of mild-to-moderate AD patients. The results suggest that not all of ADAS-Cog items are relevant for both mild and moderate AD population. This validation study demonstrates satisfactory psychometric properties of the NTB, while ADAS-Cog was found to be psychometrically inadequate.

Genome-Wide Association Study Identifies Loci and Candidate Genes for Body Composition and Meat Quality Traits in Beijing-You Chickens

Body composition and meat quality traits are important economic traits of chickens. The development of high-throughput genotyping platforms and relevant statistical methods have enabled genome-wide association studies in chickens. In order to identify molecular markers and candidate genes associated with body composition and meat quality traits, genome-wide association studies were conducted using the Illumina 60 K SNP Beadchip to genotype 724 Beijing-You chickens. For each bird, a total of 16 traits were measured, including carcass weight (CW), eviscerated weight (EW), dressing percentage, breast muscle weight (BrW) and percentage (BrP), thigh muscle weight and percentage, abdominal fat weight and percentage, dry matter and intramuscular fat contents of breast and thigh muscle, ultimate pH, and shear force of the pectoralis major muscle at 100 d of age. The SNPs that were significantly associated with the phenotypic traits were identified using both simple (GLM) and compressed mixed linear (MLM) models. For nine of ten body composition traits studied, SNPs showing genome wide significance (P<2.59E−6) have been identified. A consistent region on chicken (Gallus gallus) chromosome 4 (GGA4), including seven significant SNPs and four candidate genes (LCORL, LAP3, LDB2, TAPT1), were found to be associated with CW and EW. Another 0.65 Mb region on GGA3 for BrW and BrP was identified. After measuring the mRNA content in beast muscle for five genes located in this region, the changes in GJA1 expression were found to be consistent with that of breast muscle weight across development. It is highly possible that GJA1 is a functional gene for breast muscle development in chickens. For meat quality traits, several SNPs reaching suggestive association were identified and possible candidate genes with their functions were discussed.

Experimental designs for drug combination studies

The interest in drug combinations is growing rapidly due to the opportunities they create to increase the therapeutic effect and to reduce the frequency or magnitude of undesirable side effects when single drugs fail to deliver satisfactory results. Considerable effort in studying benefits of the joint action of drugs has been matched by the development of relevant statistical methods and tools for statistical analysis of the data obtained in such studies that allow important statistical assumptions to be taken into account, i.e. the appropriate statistical model and the distribution of the response of interest (e.g. Gaussian, Binomial, Poisson). However, much less attention has been given to the choice of suitable experimental designs for such studies, while only high quality data can ensure that the objectives of the studies will be fulfilled. Methods for construction of such experimental designs which are economical and make most efficient use of the available resources are proposed. It is shown how this can be performed when the distribution of the response is one of those belonging to the exponential family of distributions, and provide specific examples for the most common cases. In addition simple but flexible experimental designs, called ray–contour designs, are proposed. These designs are particularly useful when the use of low or high doses is undesirable and hence a standard statistical analysis of the data is not possible. Useful features of these designs are illustrated with an application in cancer study.

Knowledge, attitude and practices of HIV control measures in rural communities in Osun state. South Western Nigeria

Background: HIV epidemic is moving from urban to rural population. Assessment of the awareness of HIV/AIDS control measures in rural areas is important to determine the impact of previous and current awareness programs as well as the need for interventions. Aims & Objective: This study aimed to assess the knowledge, attitude and practices of rural dwellers in Osun State regarding HIV/AIDS and to explore the epidemiological determinants of awareness among them. Material and Methods: This is a cross sectional descriptive study. Multistage random sampling procedure was used to select the sample. The instrument of the study was a semi-structured questionnaires administered by interview to 399 respondents (sexually active men and women in the age range 15-55 years). SPSS was used for analysis and the results tabulated. Relevant statistical methods were also used to access associations where necessary and P-value of less than 0.05 was taken as significant. Results: Out of a total of 399 subjects who participated in survey, 57.9% and 36.8% are aware of VCT and ART as HIV/AIDS control measures. More than one quarter of the respondents i.e. 35.1% subjects believed HIV/AIDS is curable while only 15.5% had gone for VCT. Demographic characteristic such as educational status was found to have significant association with knowledge and attitudes towards control measures of HIV infection. Conclusion: Basic knowledge and good attitude on HIV/AIDS is still lacking among rural dwellers in Osun State. Literacy and media exposure are factors that determine awareness of HIV among them and can be helpful to raise their knowledge regarding this scourge.

The Impacts of Hospital Effluent Discharges on the Physico-chemical Water Quality of a Receiving Stream at Ile-Ife, Southwestern Nigeria

In order to contribute to the understanding of the impact of wastewater discharges from a Hospital in south-western Nigeria on the receiving water bodies, the physico-chemical qualities of the two wastewater point sources from the Obafemi Awolowo University Teaching Hospitals Complex (OAUTHC) Ile–Ife were characterized, and their impacts on the water quality of the receiving Elekete stream were assessed. Eight sampling stations were selected for the study: three, were located each on the unimpacted and impacted sections of the receiving Elekete stream while one each was located on the two wastewater point sources from OAUTHC. The physico-chemical parameters investigated include: oxygen parameters, major cations, major anions, nutrient compounds, physical parameters (temperature, turbidity, solids) as well as pH and conductivity. Samples were collected from each sampling station fortnightly for nine months and analysed using standardised laboratory methods. The results were analysed using relevant statistical methods. The result showed significant difference (P < 0.05) for all parameters between the impacted and unimpacted sections of effluent receiving stream. SO42-, Total Organic Carbon, NH4+, PO43-, and BOD5 were more than three times higher in the impacted section than in the unimpacted section while sample colour, turbidity, total suspended solids, total dissolved solids, total solids, conductivity, alkalinity, acidity, Ca2+, Mg2+, Na+, K+, Cl-, HCO3-, NO3-, and NO2- were about two times higher in the impacted section of the receiving stream than in the unimpacted section. The overall mean concentrations of 293 mg l-1 and 270 mg l-1 BOD5 in the two effluent streams indicate the medium/ strong strength of the wastewater discharges from OAUTHC. This study showed that the wastewater discharge from the (OAUTHC) Ile-Ife has significant impact on the water quality of the receiving streams. The implications are discussed.

THE NUANCES OF STATISTICALLY ANALYZING NEXT-GENERATION SEQUENCING DATA

High-throughput sequencing technologies, in particular next-generation sequencing (NGS) technologies, have emerged as the preferred approach for exploring both gene function and pathway organization. Data from NGS technologies pose new computational and statistical challenges because of their massive size, limited replicate information, large number of genes (high-dimensionality), and discrete form. They are more complex than data from previous high-throughput technologies such as microarrays. In this work we focus on the statistical issues in analyzing and modeling NGS data for selecting genes suitable for further exploration and present a brief review of the relevant statistical methods. We discuss visualization methods to assess the suitability of statistical models for these data, statistical methods for modeling differential gene expression, and methods for checking goodness of fit of the models for NGS data. We also outline areas for further research, especially in the computational, statistical, and visualization aspects of such data.

Barriers to internationalisation in SMEs: evidence from Jordan

PurposeThis study aims to identify some of the major barriers that may hinder potential small to medium‐sized enterprise (SME) exporters and non‐exporters from exporting their operations in the international market.Design/methodology/approachBased on the aim of this study, a questionnaire based survey method was conducted among 250 Jordanian manufacturing SMEs using random sampling with usable response rate of 54 per cent. Data were analysed using relevant statistical methods ranging from factor analysis to regression analysis.FindingsThe results show that economic/political‐legal and governmental barriers, financial and information barriers have a significant negative relationship with the export performance of SMEs in Jordan. Also, the results show that exporters and non‐exporters significantly agree in their views of the various barriers.Research limitations/implicationsThe study was carried out on SMEs operating in Jordan. Hence, caution should be taken when generalisation across cultures is considered. However, the findings of the study provide public and company policy makers with valuable guidelines for the formulation of suitable export marketing strategies and national export assistance programs.Originality/valueThis is ascribed to the relatively small local market size and to the country's gradual shift from heavy reliance on import substitution strategies in the last two decades to contemporary export orientation. Also, there is now a need for an urgent action plan to correct the deficit in the trade balance in the Jordanian economy. This action plan needs to include what causes Jordanian SMEs to export or prevents them from doing so. Once the relative importance of these barriers is detected, their validity in predicting the probability of a SME firm being an exporter can be tested.

Automatic Detection and Quantification of Tree-in-Bud (TIB) Opacities From CT Scans

This study presents a novel computer-assisted detection (CAD) system for automatically detecting and precisely quantifying abnormal nodular branching opacities in chest computed tomography (CT), termed tree-in-bud (TIB) opacities by radiology literature. The developed CAD system in this study is based on 1) fast localization of candidate imaging patterns using local scale information of the images, and 2) Möbius invariant feature extraction method based on learned local shape and texture properties of TIB patterns. For fast localization of candidate imaging patterns, we use ball-scale filtering and, based on the observation of the pattern of interest, a suitable scale selection is used to retain only small size patterns. Once candidate abnormality patterns are identified, we extract proposed shape features from regions where at least one candidate pattern occupies. The comparative evaluation of the proposed method with commonly used CAD methods is presented with a dataset of 60 chest CTs (laboratory confirmed 39 viral bronchiolitis human parainfluenza CTs and 21 normal chest CTs). The quantitative results are presented as the area under the receiver operator characteristics curves and a computer score (volume affected by TIB) provided as an output of the CAD system. In addition, a visual grading scheme is applied to the patient data by three well-trained radiologists. Interobserver and observer–computer agreements are obtained by the relevant statistical methods over different lung zones. Experimental results demonstrate that the proposed CAD system can achieve high detection rates with an overall accuracy of 90.96%. Moreover, correlations of observer–observer n}{}(R^2=0.8848, n}{}p< 0.01) and observer–CAD agreements n}{}(R^2=0.824, n}{}p< 0.01) validate the feasibility of the use of the proposed CAD system in detecting and quantifying TIB patterns.

The Early Years of Panel Data Econometrics

This essay focuses on the early years of panel data econometrics and two seminal papers by Yair Mundlak (1961) and Pietro Balestra and Marc Nerlove (1966). The issue of latent individual heterogeneity was identified as a central problem. One main ambition was to get a clear understanding of how differences in behavior across individuals and/or through time could and should be modeled. Another main aspect was the assumed inherent dynamic pattern of economic behavior, which requires the use of specific models and data collection. These articles attempted to build relevant models and statistical methods, mainly based on the distinction between fixed effects (analysis of covariance) and random effects. They brought back identification issues in the context of estimating a production function of sixty-six farms in Israel for 1954–58 (Mundlak 1961) and the demand for natural gas in the residential and commercial market of thirty-six U.S. states observed for 1957–62 (Balestra and Nerlove 1966).

Detecting Low Frequent Loss-of-Function Alleles in Genome Wide Association Studies with Red Hair Color as Example

Multiple loss-of-function (LOF) alleles at the same gene may influence a phenotype not only in the homozygote state when alleles are considered individually, but also in the compound heterozygote (CH) state. Such LOF alleles typically have low frequencies and moderate to large effects. Detecting such variants is of interest to the genetics community, and relevant statistical methods for detecting and quantifying their effects are sorely needed. We present a collapsed double heterozygosity (CDH) test to detect the presence of multiple LOF alleles at a gene. When causal SNPs are available, which may be the case in next generation genome sequencing studies, this CDH test has overwhelmingly higher power than single SNP analysis. When causal SNPs are not directly available such as in current GWA settings, we show the CDH test has higher power than standard single SNP analysis if tagging SNPs are in linkage disequilibrium with the underlying causal SNPs to at least a moderate degree (r2>0.1). The test is implemented for genome-wide analysis in the publically available software package GenABEL which is based on a sliding window approach. We provide the proof of principle by conducting a genome-wide CDH analysis of red hair color, a trait known to be influenced by multiple loss-of-function alleles, in a total of 7,732 Dutch individuals with hair color ascertained. The association signals at the MC1R gene locus from CDH were uniformly more significant than traditional GWA analyses (the most significant P for CDH = 3.11×10−142 vs. P for rs258322 = 1.33×10−66). The CDH test will contribute towards finding rare LOF variants in GWAS and sequencing studies.

Characteristics of meta-analyses and their component studies in the Cochrane Database of Systematic Reviews: a cross-sectional, descriptive analysis

BackgroundCochrane systematic reviews collate and summarise studies of the effects of healthcare interventions. The characteristics of these reviews and the meta-analyses and individual studies they contain provide insights into the nature of healthcare research and important context for the development of relevant statistical and other methods.MethodsWe classified every meta-analysis with at least two studies in every review in the January 2008 issue of the Cochrane Database of Systematic Reviews (CDSR) according to the medical specialty, the types of interventions being compared and the type of outcome. We provide descriptive statistics for numbers of meta-analyses, numbers of component studies and sample sizes of component studies, broken down by these categories.ResultsWe included 2321 reviews containing 22,453 meta-analyses, which themselves consist of data from 112,600 individual studies (which may appear in more than one meta-analysis). Meta-analyses in the areas of gynaecology, pregnancy and childbirth (21%), mental health (13%) and respiratory diseases (13%) are well represented in the CDSR. Most meta-analyses address drugs, either with a control or placebo group (37%) or in a comparison with another drug (25%). The median number of meta-analyses per review is six (inter-quartile range 3 to 12). The median number of studies included in the meta-analyses with at least two studies is three (inter-quartile range 2 to 6). Sample sizes of individual studies range from 2 to 1,242,071, with a median of 91 participants.DiscussionIt is clear that the numbers of studies eligible for meta-analyses are typically very small for all medical areas, outcomes and interventions covered by Cochrane reviews. This highlights the particular importance of suitable methods for the meta-analysis of small data sets. There was little variation in number of studies per meta-analysis across medical areas, across outcome data types or across types of interventions being compared.

P1-410 Evaluation of infant mortality risk factors in an Eastern area of Iran; a case-control study- 2009

IntroductionInfant Mortality Rate (IMR) is one of the most important indicators of community health situation and especially children health status. This study was conducted for determination of IMR risk factors...

Self-organized criticality judgment and extreme statistics analysis of major urban fires

The spatial (economic loss) and temporal characteristics of urban fires were analyzed employing relevant statistical methods. A fractal structure in terms of the power-law relation between fire frequency and economic loss was found on a spatial scale, and an exponential relation between frequency and time interval was found on a temporal scale. Thus, urban fire does not meet the rigorous criteria of self-organized criticality. In addition, based on the spatial power-law distribution characteristics, a correlation model of the frequency and scale of loss due to urban fire was established using the extremum statistical method. This model was then applied to the case analysis of Hefei and the probability of major fire incidents in the future was predicted.

Oncological screening for Bilateral Breast Reduction: A survey of practice variations in UK Breast and Plastics surgeons 2009

Bilateral Breast Reduction (BBR) is a common procedure performed by Breast and Plastic surgeons in the UK. No consensus exists regarding preoperative screening for malignancy or for selective criteria for such screening. Preoperative BBR screening practices among UK Breast and Plastic surgeons are unknown. Ascertain the preoperative and postoperative BBR screening practices of UK Breast and Plastic surgeons. A questionnaire was posted to all 434 Breast and 335 Plastic surgeons in the UK. All results were analysed with relevant statistical methods. 64% of Breast surgeons and 72% of Plastic surgeons responded. 40% of Breast surgeons and 91% of Plastic surgeons perform BBR. Routine radiological screening: 92% Breast 41% Plastic (p<0.05). Routine breast examination prior to BBR: 98% Breast 91% Plastic. Routine histology for BBR specimens: 96% Breast 90% Plastic. Selective screening of patients aged 30-40 years old: Breast 38% Plastic 10%. Selective screening of patients aged 40-50: Breast 78%, Plastic 53%. Selective screening of patients with strong family history of breast cancer: Breast 72%, Plastic 91%. Selective screening of patients with previous breast cancer: Breast 77%, Plastic 93%. There are significant differences in practice between UK Breast surgeons and Plastic surgeons in preoperative oncological screening for BBR. The large discrepancy in preoperative radiological screening, reflects a ubiquitous pro-screening ideology among Breast surgeons not prevalent among Plastic surgeons. These results will provoke debate towards the direction of consensus to ultimately reflect best practice.

A comprehensive approach to plume stability

AbstractThis article defines and presents a systematic approach to groundwater plume‐stability assessment. Qualitative and quantitative methods that have been used to assess plume stability at National Priority List sites undergoing optimization are reviewed. Example case studies are included to illustrate the advantages of combining multiple analysis methods. Relevant statistical methods include identifying normal data distributions, detection frequencies, coefficients of variation, individual well trends, and rates of change at individual monitoring locations. Trend estimates for total plume mass and center of mass provide a broader picture of plumewide processes. Deterministic methods, such as quantitative mass‐balance approaches, may be useful for larger plumes. Qualitative assessments include evaluations of the conceptual site model, source strength, attenuation mechanisms, and hydrogeology. Because groundwater plumes are always dynamic, the determination of plume stability has to include qualitative steps relating the rate and magnitude of change to the goals and objectives of the program and the time frame over which critical management decisions are to be made. The assessment of plume stability is, therefore, presented as a process that should involve both qualitative and quantitative steps for determining the acceptability of variability in groundwater contaminant concentrations. © 2010 Wiley Periodicals, Inc.