Basic Definitions in Probability and Statistics
The use of frequency distributions and measure of variability are among the simplest aspects of statistics. Uncovering the existence of variability and its underlying causes in any operation is essentially application of the science of statistical quality control. The total sources of product variability, when reduced to their practical minimum, can be grouped together and are referred to as the system’s “inherent variability.” The average of the frequency distribution is computed by multiplying the frequency of occurrence by the recorded dimension, and dividing the sum of the products by the number of units measured. The information from a frequency distribution can be used to establish process control limits from which a system of statistical quality control can be developed around such control charts. When the probability distributions of one or more variables are given, it is possible to determine distributions of other random variables which depend on them in some way.