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Confidence intervals are in many ways Keywords: bootstrap; confidence interval; hypothesis test; resampling; statisticsResearch in the organizational sciences makes frequent use of statistical inferences. These inferences often take the form of null hypothesis tests based on mathematical probability theory. We want to know whether the mean of one group differs from the mean of another group, or whether two variables are correlated, or if a parameter in a regression model differs from zero.This article explains and discusses the idea of a bootstrap percentile confidence interval-which is an alternative to many of these methods. Furthermore, it is an alternative with substantial advantages over the usual methods. These advantages fall into two separate categories.The first stems from the use of confidence intervals in place of significance levels (p values) and null hypotheses. Instead of, for example, testing the hypothesis that there is no difference between the means of two populations, and citing the resulting significance level, we can set up an interval estimate for the difference of the two means. This has a number of advantages, which are briefly explained in the next section.The second category of advantages are those due to using the method of bootstrapping in place of conventional methods to derive confidence intervals. This is the main subject of this article. This second category of advantages divides into three subcategories:
Bootstrap confidence intervals provide a way of quantifying the uncertainties in the inferences that can be drawn from a sample of data. The idea is to use a simulation, based on the actual data, to estimate the likely extent of sampling error. Michael Wood explains how simple bootstrapping works and explores some of its advantages.
OBJECTIVES-Changes in mucosal serotonin (5-HT) signaling have been detected in a number of functional and inflammatory disorders of the gastrointestinal tract. This study was undertaken to determine whether chronic constipation (CC) is associated with disordered 5-HT signaling and to evaluate whether constipation caused by opiate use causes such changes.METHODS-Human rectal biopsy samples were obtained from healthy volunteers, individuals with idiopathic CC, and individuals taking opiate medication with or without constipation. EC cells were identified by 5-HT immunohistochemistry. 5-HT content and 5-HT release levels were determined Correspondence: Gary M. Mawe, Ph.D., D403A Given Building, Department of Anatomy and Neurobiology, University of Vermont, Burlington, VT, USA 05405, (802) 656-8257 (phone), (802) 656-8704 (fax), gary.mawe@uvm.edu. * MMC and MDC contributed equally to this work, with MMC concentrating primarily on the chronic constipation arm of the study and MDC working primarily on the opiate constipation experiments. Conflict of interest items 1. Guarantor of the manuscriptGary M. Mawe, PhD 2. Roles of each author Meagan M Costedio: patient screening, obtaining consent, tissue acquisition, tissue processing, data analysis, and manuscript preparation and editing Matthew D Coates: patient screening, obtaining consent, tissue acquisition, tissue processing, data analysis, and manuscript preparation and editing Elice M Brooks: tissue acquisition, data acquisition, and data analysis Lisa M Glass: data acquisition, and data analysis. Eric K Ganguly: aided in conception of the project, acquiring IRB approval, obtaining informed consent, and tissue acquisition. Hagen Blaszyk: evaluation of sections and blind scoring of inflammation levels in the chronic constipation component of the study Allison L. Ciolino: evaluation of sections and blind scoring of inflammation levels in the opiate constipation component of the study Michael J Wood: involved in obtaining informed consent, and tissue acquisition. Doris Strader: involved in obtaining informed consent, and tissue acquisition. Neil H Hyman: involved in study conceptualization, planning, and identifying potential candidates for the chronic constipation component of the study. Peter L Moses: involved in study conceptualization, planning, obtaining informed consent, and tissue acquisition, data analysis, and manuscript preparation and editing Gary M Mawe: involved in study conceptualization, planning, data analysis, and manuscript preparation and editing. All authors reviewed and approved the manuscript prior to submission. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript by enzyme immunoassay, and mRNA levels for the synthetic enzyme, tryptophan hydroxylase 1 (TpH1) and the serotonin transporter (SERT) were assessed by quantitative real-time RT-PCR.RESULTS-CC was associated with increases in TpH1 transcript, 5-HT content, and 5-HT release under basal and stimulated conditions, whereas EC cell numbers and SERT transcript leve...
The management of intrathoracic esophageal perforation with delayed diagnosis is a subject of controversy. Because of the obvious advantages of primary repair as a simple single-stage operation, this technique was preferentially used to treat 18 of 22 consecutive patients with esophageal perforation. These patients were stratified into three groups according to the time interval between perforation and repair: group A, less than 6 hours, five patients (28%); group B, 6 to 24 hours, six patients (33%); and group C, more than 24 hours, seven patients (39%). Group A patients were older (p < 0.05) and group B had fewer iatrogenic perforations (B, 17%; A, 80%; C, 57%, p < 0.1). Additional tissue was used to buttress the repair site in all three groups (A, 3/5 patients, 60%; B, 4/6 patients, 67%; C, 6/7 patients, 86%; p = not significant). In seven patients (39%), a fundic wrap was used to reinforce the site of primary repair. The outcomes of the three groups were analyzed. Group A had the lowest proportion of postoperative leaks (A, 0/4 patients, 0%; B, 4/6 patients, 67%; C, 5/6 patients, 83%; p < 0.05) and postoperative morbidity (A, 2/5 patients, 40%; B, 6/6 patients, 100%; C, 6/7 patients, 86%; p < 0.1). However the increased incidence of leak and morbidity did not lead to an increase in mortality. One death occurred in each group, with an overall mortality of 17% (A, 1/5 patients, 20%; B, 1/6 patients, 17%; C, 1/7 patients, 14%; p = not significant). We conclude that in the era of advanced intensive care capabilities, primary repair of intrathoracic esophageal perforation can be safely accomplished in most patients regardless of the time interval between perforation and operation. Leakage at the suture site is common unless primary repair is carried out without delay. Postoperative leakage, however, is usually inconsequential and does not necessarily result in an adverse outcome.
BackgroundMale circumcision (MC) reduces HIV acquisition and is a key public health intervention in settings with high HIV prevalence, heterosexual transmission and low MC rates. In Papua New Guinea (PNG), where HIV prevalence is 0.8%, there is no medical MC program for HIV prevention. There are however many different foreskin cutting practices across the country’s 800 language groups. The major form exposes the glans but does not remove the foreskin. This study aimed to describe and quantify foreskin cutting styles, practices and beliefs. It also aimed to assess the acceptability of MC for HIV prevention in PNG.MethodsCross-sectional multicentre study, at two university campuses (Madang Province and National Capital District) and at two ‘rural development’ sites (mining site Enga Province; palm-oil plantation in Oro Province). Structured questionnaires were completed by participants originating from all regions of PNG who were resident at each site for study or work.ResultsQuestionnaires were completed by 861 men and 519 women. Of men, 47% reported a longitudinal foreskin cut (cut through the dorsal surface to expose the glans but foreskin not removed); 43% reported no foreskin cut; and 10% a circumferential foreskin cut (complete removal). Frequency and type of cut varied significantly by region of origin (p < .001). Most men (72-82%) were cut between the ages of 10 – 20 years. Longitudinal cuts were most often done in a village by a friend, with circumferential cuts most often done in a clinic by a health professional. Most uncut men (71%) and longitudinal cut men (84%) stated they would remove their foreskin if it reduced the risk of HIV infection. More than 95% of uncut men and 97% of longitudinal cut men would prefer the procedure in a clinic or hospital. Most men (90%) and women (74%) stated they would remove the foreskin of their son if it reduced the risk of HIV infection.ConclusionAlthough 57% of men reported some form of foreskin cut only 10% reported the complete removal of the foreskin, the procedure on which international HIV prevention strategies are based. The acceptability of MC (complete foreskin removal) is high among men (for themselves and their sons) and women (for their sons). Potential MC services need to be responsive to the diversity of beliefs and practices and consider health system constraints. A concerted research effort to investigate the potential protective effects of longitudinal cuts for HIV acquisition is essential given the scale of longitudinal cuts in PNG.
The techniques of statistical process control (SPC) are designed to monitor production processes in order to prevent the production of waste and improve the quality of future output. The emphasis is on the prevention of problems before they occur instead of simply revealing and correcting past mistakes. SPC is now increasingly used for service processes as well as the manufacturing processes for which it was originally developed. This raises the question of whether the same benefits can be achieved, and whether the techniques need to be refined in any way, if they are to be equally useful in the service arena. Looks at a number of examples of the application of SPC techniques to service processes. Argues that there are features of many service processes which have implications for the way SPC should be applied. Proposes a set of guidelines for systems for the statistical monitoring of service processes. Argues that standard SPC techniques can yield substantial benefits for service processes, provided that users remember these guidelines. In particular, argues that the use of the word “control”, and so the phrase “statistical process control”, is often inappropriate. Finally, suggests that some of the conclusions may be equally applicable to many production processes.
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