INTRODUCTION

To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of.

Ronald Fisher

Chapter Objectives

When you have completed this chapter, you will be able to understand:

• What biostatistics is and its application in medical science

• Some basic elements of biostatistics

• What variables and data are

• Different types of data and their practical utility

• Different data measurement scales and their application

• Various presentations of data—text, tables, and charts

• The broad subdivisions of statistics—descriptive and inferential

• Descriptive statistics and the concept of central tendency and dispersion

• Various measures of central tendency—the mean, median, and mode—and their practical application

• Various measures of dispersion—the range, distribution, percentile and interquartile range, standard deviation, standard error—and their practical application

In contrast to material sciences like physics and mathematics, which are deductive, biomedical science is inductive. It is a science of approximation, where observations are recognized, collected, and compiled to provide answers and predict future occurrences. It is based on the process of recognizing patterns of different incidents as they are observed, with an attempt to arrive at logical conclusions and converting these into knowledge. However, the methods by which such observations (or information) are converted into knowledge should follow some objective norms. Statistics is a process by which numerical data are objectively transformed and summarized into a usable form,1 and inferences can be made about specific random phenomena on the basis of relatively limited sample material.2 Biostatistics is the branch of applied statistics that applies statistical methods to medical and biologic problems3 in order to make decisions when analyzing biomedical data. In other words, biostatistics is the process by which medical and other biologic observations are objectively converted into knowledge.4 The principal functions of statistics, or biostatistics (Figure 9-1) are to: (i) collect, organize, summarize, and to analyze the findings or data and (ii) draw general conclusions or inferences from the observation on a smaller part of that data about a large body of data.2 The former is known as “descriptive statistics,” while the latter is known as “statistical inference,” or “inferential statistics” (Box 9-1).

FIGURE 9-1

Statistical Data and the Relation between Descriptive and Inferential Statistics. Adapted from Driscoll et al.1 BOX 9-1 Biostatistics and Its Broad Subdivisions

• Statistics is a process by which numerical data are transformed into a usable form for scientific interpretation so that inferences can be made about specific random phenomena on the basis of relatively limited sample material.

• Biostatistics is the branch of statistics that applies statistical methods to medical and biologic problems to make decisions when analyzing biomedical data.

• Descriptive statistics teaches how to collect, organize, and summarize data.

• Inferential statistics (or statistical inference) teaches ...

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