A geometric interpretation of the permutation pp-value and its application in eQTL studies

Permutation $p$-values have been widely used to assess the significance of linkage or association in genetic studies. However, the application in large-scale studies is hindered by a heavy computational burden. We propose a geometric interpretation of permutation $p$-values, and based on this geometric interpretation, we develop an efficient permutation $p$-value estimation method in the context of regression with binary predictors. An application to a study of gene expression quantitative trait loci (eQTL) shows that our method provides reliable estimates of permutation $p$-values while requiring less than 5% of the computational time compared with direct permutations. In fact, our method takes a constant time to estimate permutation $p$-values, no matter how small the $p$-value. Our method enables a study of the relationship between nominal $p$-values and permutation $p$-values in a wide range, and provides a geometric perspective on the effective number of independent tests.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS298 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Consistent Testing for Recurrent Genomic Aberrations

Genomic aberrations, such as somatic copy number alterations, are frequently observed in tumor tissue. Recurrent aberrations, occurring in the same region across multiple subjects, are of interest because they may highlight genes associated with tumor development or progression. A number of tools have been proposed to assess the statistical significance of recurrent DNA copy number aberrations, but their statistical properties have not been carefully studied. Cyclic shift testing, a permutation procedure using independent random shifts of genomic marker observations on the genome, has been proposed to identify recurrent aberrations, and is potentially useful for a wider variety of purposes, including identifying regions with methylation aberrations or overrepresented in disease association studies. For data following a countable-state Markov model, we prove the asymptotic validity of cyclic shift $p$-values under a fixed sample size regime as the number of observed markers tends to infinity. We illustrate cyclic shift testing for a variety of data types, producing biologically relevant findings for three publicly available datasets.Comment: 35 pages, 7 figure

Customer relationship management for brand commitment and brand loyalty

This article examined the impact of customer relationship management strategy on customers brand commitment and brand loyalty in the Nigeria financial sector. Methodology: the positivist quantitative survey approach was used to collect primary for this research. Simple random sampling was used to select 250 customers of Nigerian deposit accepting banks. Findings: the study found that CRM strategy impacts positively on banks’customers brand commitment and loyalty behaviours. However, continuance loyalty weighted highly positive on customer advocacy behaviour than affective loyalty. Conclusions: the study concluded that customer relationship management strategy helps in winning customers brand commitment and loyalty. Thus, continuance factors are suitable for predicting advocacy intentions of customers of Nigerian banks. Recommendations: the study recommended for strategic policy makers in the Nigeria financial sector to improve on their firms’ CRM infrastructure in order to continually meet customers’ expectations. KEYWORDS: Customer relationship management, customer advocacy, brand commitment, loyalt

A statistical framework for testing functional categories in microarray data

Ready access to emerging databases of gene annotation and functional pathways has shifted assessments of differential expression in DNA microarray studies from single genes to groups of genes with shared biological function. This paper takes a critical look at existing methods for assessing the differential expression of a group of genes (functional category), and provides some suggestions for improved performance. We begin by presenting a general framework, in which the set of genes in a functional category is compared to the complementary set of genes on the array. The framework includes tests for overrepresentation of a category within a list of significant genes, and methods that consider continuous measures of differential expression. Existing tests are divided into two classes. Class 1 tests assume gene-specific measures of differential expression are independent, despite overwhelming evidence of positive correlation. Analytic and simulated results are presented that demonstrate Class 1 tests are strongly anti-conservative in practice. Class 2 tests account for gene correlation, typically through array permutation that by construction has proper Type I error control for the induced null. However, both Class 1 and Class 2 tests use a null hypothesis that all genes have the same degree of differential expression. We introduce a more sensible and general (Class 3) null under which the profile of differential expression is the same within the category and complement. Under this broader null, Class 2 tests are shown to be conservative. We propose standard bootstrap methods for testing against the Class 3 null and demonstrate they provide valid Type I error control and more power than array permutation in simulated datasets and real microarray experiments.Comment: Published in at http://dx.doi.org/10.1214/07-AOAS146 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Sites and mechanisms of potassium transport along the renal tubule

Renal tubules are capable of transporting potassium in both reabsorptive and secretory directions. Reabsorption is the principal process in the proximal portions of the nephron, whereas in the more distal segments secretion usually dominates.a That most potassium excreted by the kidney is not derived from filtered potassium, but is actually secreted, was indicated by clearance [1,2] and stop-flow experiments [3–5], and ultimately confirmed by measurements made on tubule fluid samples obtained by microcatheterization [6] and by micropuncture [7–9]. The distinction between proximal reabsorption and distal secretion should not be overdrawn, however. Some secretion occurs in segments of the proximal part of the nephron, and reabsorption appears to occur along the collecting duct. Thus, although secretion by cells of the distal nephron is recognized as the main process regulating the rate of potassium excretion, other secretory and reabsorptive processes may modify the total amount of excreted potassium and, in so doing, may affect the simultaneous transport rates of water and other electrolytes.Evidence establishing numerous features of the several processes regulating renal potassium excretion, particularly the distal secretory processes, has been reviewed extensively [10–20], A picture has emerged from experimental work that to some extent explains changes seen in the rates of renal potassium excretion in response to a number of factors, including potassium intake, sodium excretion, miner-alocorticoids, hydration, acid-base balance, and the anion composition of plasma. As will become evident, however, the exact secretory site or sites along the distal nephron affected by these factors and the nature of the cellular mechanisms involved are still not known with certainty. Recent structural and biochemical observations from experiments with isolated tubule fragments have provided some additional insights into the questions both of transport sites and transport mechanisms. In the following this information will be incorporated—at times quite speculatively—into our present understanding of renal potassium transport across different segments of the renal tubule system.aReabsorption means net transport from lumen to blood, and secretion means net transport from blood to lumen — mechanism is not specified. Nephron is used in the general sense, meaning the tubule system from the glomerulus to the end of the collecting system

Customer Relationship Management and Service Quality: a qualitative study

This study examined customer relationship management effectiveness and Service quality on international customers in a single University in the UK higher education sector. We adopted the qualitative research design with focus group interview approach. Focus group discussions were carried out with twelve purposively sample units of analysis from the case University. The study primary data was analysed using thematic template technique with Nvivo 10. The study found that the CRM programme of the case University is effective following the various students‟ oriented social and academic programs. Findings also showed that its CRM program influenced international students‟ satisfaction and positive advocacy behaviour. The study found six emerging themes for evaluating customer relationship management effectiveness in the higher education sector. Thus, recommended the need for strategic policy makers in the higher education sector to enhance investments on building stronger customer relationship management infrastructure.KEYWORDS: Customer Relationship Management, Service Quality, Qualitative Stud