Data needs to be understood. There are two characteristics of data and these include dispersion and central tendency. Data as a tendency to be centered around a point called average which has a crucial bearing on probability in the realm of project management.
As a property of the central limit theorem, the central tendency predicts data observations in a particular distribution that tend to gather around a central location. These include measurements such as mean (average), median (middle value) and mode (most expected number to occur).
The three measures of central tendency give summary measures to describe the entire set of data using a single value. This value represents the center of the data distribution. It is important to take note that once the data is normally distributed, all three measurements should arrive at an identical value. It indicates that all measurements are effective in showing the typical value of the entire data set.
While it is important to look at the central tendency of data, looking at its dispersion such as the range, quartiles and standard deviation are also critical in determining the probability and level of confidence of the data set.
This project management term is defined in the 5th edition of the PMBOK.