Association versus causation

This functional definition of Statistics may well contain some concepts and terms with which you are not familiar at this point, and that is fine. This book s goal is to make you familiar with these terms and concepts so that you will understand the statistical processes and procedures that are used in clinical trials. Individual chapters address different parts of this definition. However, it is important for us to emphasize here that the individual aspects presented in the chapters are really seamless components of one overall experimental approach to gaining knowledge, the discipline of Statistics. These components act together to ensure that high-quality data acquisition, correct analysis, and appropriate interpretations provide optimal answers to good research questions. 

The word statistics with a lower case s is used throughout the book as simply the plural of the term statistic. A listing of the sports team s wins and losses for the last 10 seasons, perhaps along with similar details for every other team in the same division or conference, would very adequately be described as statistics. 

The term statistical analysis has two meanings. Statistical analysis, used in a general sense, can be regarded as a global description or plan of how data collected will be analyzed. The term a statistical analysis refers to an individual analytical technique that is used to describe and analyze numerical information. This book teaches you how to conduct a collection of statistical analyses that are appropriate for use in analyzing the results of clinical trials. 

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The remainder of this chapter discusses the evidence for the various causal relationships between Pb exposure and toxicity and disease. As set forth in Table 21.2, adverse human health effects of lead are placed in causal context using the nine proofs-of-causality criteria first enunciated by British medical statistician Sir Austin Bradford Hill in 1965 and subsequently labeled Hill s Criteria of Causation. These criteria are relevant and of particular value in the environmental epidemiology of Pb, given the many contentious arguments over association versus cause that have been lodged against Pb s human health impacts, particularly in earlier eras of lead health research and in the evolution of Pb as a major public health factor. 

Nevertheless, depressive episodes among alcohol-dependent men and women are heterogeneous in terms of both causation and clinical course. Studies have shown differences between patients with the onset of major depression before alcohol dependence or during a long abstinence period (i.e., independent major depression) versus those who experience depressive symptoms only in association with alcohol use ( 34). Specifically, the former are more likely to ... 

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