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Introduction to Biostatistics
01 Jan 1973-
TL;DR: In this article, the authors introduce the concept of biostatistics and introduce the Biostatistic Approach to Biometrics (BAPB) as a method for biometrics.
Abstract: Introduction to Biostatistics , Introduction to Biostatistics , کتابخانه مرکزی دانشگاه علوم پزشکی تهران
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TL;DR: The aim in this forum article is to argue for the greater use of the last of these tests, the t-test for unequal variances, which is not commonly used.
Abstract: Often in the study of behavioral ecology, and more widely in science, we require to statistically test whether the central tendencies (mean or median) of 2 groups are different from each other on the basis of samples of the 2 groups. In surveying recent issues of Behavioral Ecology (Volume 16, issues 1–5), I found that, of the 130 papers, 33 (25%) used at least one statistical comparison of this sort. Three different tests were used to make this comparison: Student’s t-test (67 occasions; 26 papers), Mann–Whitney U test (43 occasions; 21 papers), and the t-test for unequal variances (9 occasions; 4 papers). My aim in this forum article is to argue for the greater use of the last of these tests. The numbers just related suggest that this test is not commonly used. In my survey, I was able to identify tests described simply as ‘‘t-tests’’ with confidence as either a Student’s t-test or an unequal variance t-test because the calculation of degrees of freedom from the 2 sample sizes is different for the 2 tests (see below). Hence, the neglect of the unequal variance t-test illustrated above is a real phenomenon and can be explained in several (nonexclusive ways) ways: 1. Authors are unaware that Student’s t-test is unreliable
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917 citations
TL;DR: In this paper, it is shown that the ROC area is equivalent to the Mann-Whitney U-statistic testing the significance of forecast event probabilities for cases where events actually occurred with those where events did not occur.
Abstract: The areas beneath the relative (or receiver) operating characteristics (ROC) and relative operating levels (ROL) curves can be used as summary measures of forecast quality, but statistical significance tests for these areas are conducted infrequently in the atmospheric sciences. A development of signal-detection theory, the ROC curve has been widely applied in the medical and psychology fields where significance tests and relationships to other common statistical methods have been established and described. This valuable literature appears to be largely unknown to the atmospheric sciences where applications of ROC and related techniques are becoming more common. This paper presents a survey of that literature with a focus on the interpretation of the ROC area in the field of forecast verification. We extend these foundations to demonstrate that similar principles can be applied to the interpretation and significance testing of the ROL area. It is shown that the ROC area is equivalent to the Mann–Whitney U-statistic testing the significance of forecast event probabilities for cases where events actually occurred with those where events did not occur. A similar derivation shows that the ROL area is equivalent to the Mann–Whitney U-statistic testing the magnitude of events with respect to whether or not an event has been forecast. Because the Mann–Whitney U-statistic follows a known probability distribution, under certain assumptions it can be used to define the statistical significance of ROC and ROL areas and for comparing the areas of competing forecasts. For large samples the significance of either measure can be accurately assessed using a normal-distribution approximation. Copyright © 2002 Royal Meteorological Society
757 citations
TL;DR: In antimicrobial investigations, using inverted petriplate and food poison techniques, the leaf and bark volatile oils has been found to be highly effective against all the tested fungi except Aspergillus ochraceus, however, leaf oleoresin has shown inhibition only for Penicillium citrinum whereas bark olerosin has caused complete mycelial zone inhibition for As pergillus flavus and A. och raceus.
587 citations
TL;DR: The visual receptive field physiology and anatomical connections of the lateral intraparietal area (area LIP), a visuomotor area in the lateral bank of the inferior parietal lobule, were investigated in the cynomolgus monkey.
Abstract: The visual receptive field physiology and anatomical connections of the lateral intraparietal area (area LIP), a visuomotor area in the lateral bank of the inferior parietal lobule, were investigated in the cynomolgus monkey (Macaca fascicularis). Afferent input and physiological properties of area 5 neurons in the medial bank of the intraparietal sulcus (i.e., area PEa) were also determined. Area LIP is composed of two myeloarchitectonic zones: a ventral zone (LIPv), which is densely myelinated, and a lightly myelinated dorsal zone (LIPd) adjacent to visual area 7a. Previous single-unit recording studies in our laboratory have characterized visuomotor properties of area LIP neurons, including many neurons with powerful saccade-related activity. In the first part of the present study, single-unit recordings were used to map visual receptive fields from neurons in the two myeloarchitectonic zones of LIP. Receptive field size and eccentricity were compared to those in adjacent area 7a. The second part of the study investigated the cortico-cortical connections of area LIP neurons using tritiated amino acid injections and fluorescent retrograde tracers placed directly into different rostrocaudal and dorsoventral parts of area LIP. The approach to area LIP was through somatosensory area 5, which eliminated the possibility of diffusion of tracers into area 7a. Unlike many area 7a receptive fields, which are large and bilateral, area LIP receptive fields were much smaller and exclusively confined to the contralateral visual field. In area LIP, an orderly progression in visual receptive fields was evident as the recording electrode moved tangentially to the cortical surface and through the depths of area LIP. The overall visual receptive field organization, however, yielded only a rough topography with some duplications in receptive field representation within a given rostrocaudal or dorsoventral part of LIP. The central visual field representation was generally located more dorsally and the peripheral visual field more ventrally within the sulcus. The lower visual field was represented more anteriorly and the upper visual field more posteriorly. In LIP, receptive field size increased with eccentricity but with much variability with in the sample. Area LIPv was found to have reciprocal cortico-cortical connections with many extrastriate visual areas, including the parieto-occipital visual area PO; areas V3, V3A, and V4: the middle temporal area (MT); the middle superior temporal area (MST); dorsal prelunate area (DP); and area TEO (the occipital division of the intratemporal cortex). Area LIPv is also connected to area TF in the lateral posterior parahippocampal gyrus.(ABSTRACT TRUNCATED AT 400 WORDS)
565 citations