Measures of Variation

A population is all the data that exist for a process. A sample is a small group of data randomly taken from a population that is representative of the whole population.

Three statistical measures of variation are:

Mean—The arithmetic average of the sample. This measures the location of the process output.

Range—The highest data point minus the lowest data point. This is one of two measures of the variation in the process.

Standard Deviation—A statistic that measures how data cluster around the mean. This is another measure of variation.

The smaller the standard deviation, the less variation there is in a process. The larger the standard deviation, the more variation there is in a process.