Statistics II: Central tendency and spread of data

Examining the raw data is an essential first step before proceeding to statistical analysis. Thereafter, two key sample statistics that may be calculated from a dataset are a measure of the central tendency of the sample distribution and of the spread of the data about this central tendency. Inferential statistical analysis is dependent on a knowledge of these descriptive statistics. In the first article of this series, types of data and correlations were discussed. Different measures of central tendency attempt to determine what might variously be termed the typical, normal, expected or average value of a dataset. Three of them are in general use for most types of data: the mode, median, and mean.