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Biostatistics seeks to answer the question "Is there a difference?" in the rate of a disease or characteristic among subgroups of patients. The goal of this article is to introduce and define measures used in epidemiology and discuss different types of analyses in clinical research with an emphasis on the concepts and implications of the analyses rather than the mathematics. The implications of the use of measures such as incidence and prevalence, as well as odds, risk, and hazards ratios may affect study conclusions. An understanding of the distinction between these summary measures is essential. The concepts of univariate and multivariate analyses, a discussion of what it means to control for potential confounders, and a description of statistical power and significance are also presented. These concepts are integral to the design and analysis of clinical studies. An understanding of their advantages and applications will enhance the reader's ability to understand and evaluate the literature.

Epidemiology is the basic medical science that focuses on the distribution and determinants of disease frequency in human populations. An understanding of the tools of epidemiology is helpful in defining the limitations of medical research and evaluating the conclusions of studies. This is the second in a series of three articles whose objective is to present the basic concepts of epidemiology and biostatistics, highlighted by examples of these concepts applied in the medical literature studying patients receiving dialysis. This article describes the study designs of case-control, cohort, and randomized trials and issues in the conduct and analysis of each. Several studies examining the association between hematocrit and survival of dialysis patients are discussed. Their differences in design and methods are discussed in the context of their effect on study conclusions. The goal of this article is to present the reader with the issues of study design and the limitations they impose on study conclusions. Through the examination of these methods, the reader will be able to rigorously examine study methods and understand how design affects study conclusions and their application to patient care. [ABSTRACT FROM AUTHOR]

Epidemiology is the basic medical science that focuses on the distribution and determinants of disease frequency in human populations. An understanding of the tools of epidemiology is helpful in defining the limitations of medical research and evaluating the conclusions of studies. This is the first in a series of three articles whose objective will be to present the basic concepts of epidemiology and biostatistics. Examples of each of the tools and limitations discussed from studies of patients with end-stage renal disease (ESRD) will be presented to provide the reader with a practical application of the concepts. This series of articles will help the reader to weigh methods and study designs to understand the appropriate conclusions that may be drawn from any data. [ABSTRACT FROM AUTHOR]