Descriptive Statistics

Data come from the samples we take from a population. In statistics, we deal with the sample that we collect and make our decisions. This chapter presents a summary of a number of basic descriptive statistics, such as the measures of central tendency and measures of variation. It discusses what is referred to as measures of central tendency. As mean, median, and mode describe only some sample characteristics, the chapter discusses several forms of variance and relates them to data accordingly. The chapter illustrates a study whose objective was to determine the long-term within- and between-laboratory variation of cortisol, ferritin, thyroxine, free thyroxine, and Thyroid-Stimulating Hormone (TSH) measurements by using commonly available methods and to determine if these variations are within accepted medical standards, that is to say within the specified coefficient of variation (CV). It focuses on the CV for one of the analytes, namely, the TSH.