Is the central tendency of a sample of values, taken as the sum of the values divided by the size of the sample, i.e., the number of observations.

The numerical value separating the higher half of a data set from the lower half.

A genre of RPG games in which a very large number of players interact with one another within a virtual world.

A frequently used and usually more practical, random sampling method. It is particularly useful in situations for which no list of the elements within a population is available and therefore cannot be selected directly. As this form of sampling is conducted by randomly selecting subgroups of the population, possibly in several stages, it should produce results equivalent to a simple random sampling strategy.