ABSTRACT
The concept of sampling is neither new nor unfamiliar in everyday life. A cook examines a few grains of rice to find whether nearly all of them are properly cooked or not. In medicine, study of blood, urine, stool, and sputum samples, and biopsy specimens is common. This chapter deals primarily with subjects, mostly human beings but sometimes laboratory animals, who have great intrinsic biologic variability.
This Chapter The chapter begins with an explanation in Section 3.1 of terms and concepts that are
typical to sampling. This also includes a discussion on the advantages and limitations of sampling. The aim of the sampling method is to choose a fraction that adequately represents the entire spectrum of the target subjects. The purpose of sampling is to extrapolate the results to a substantially larger population. Various common methods of random sampling that could meet this aim are discussed in Section 3.2. Some other methods, including nonrandommethods, are presented in Section 3.3. Some examples of sample survey are given in Section 3.4. These examplesmay help one appreciate the practical applications of sampling and data collection methods. The literature on sampling methods is extensive. For statistical details of these
methods, see Thompson [1]. Even though the description in this chapter is brief, it is sufficient to explain the basics of sampling methods. The notations used here are those that are conventionally used in texts that deal with sampling and are sometimes different from those used in later chapters of this book.
