4.1. Measures of Central Tendency
Although the graphs discussed in Chapter 3, “Presenting Data in Charts and Tables,” are extremely useful for getting a visual picture of what the distribution of a CTQ or CTP looks like, you need to compute measures of central tendency or location. Three measures of central tendency will be developed: the arithmetic mean (often called the mean or average), the median, and the mode. If you compute these measures from a sample, they are statistics. If you compute these measures from a population, they are parameters. (To distinguish sample statistics and population parameters, Roman letters are used for sample statistics, and Greek letters are used for population parameters.)
The Arithmetic Mean
The arithmetic ...