Overview
An investigation typically focus on a pre-defined collection of objects constituting
a population of interest. Mostly, a subset of the population, called sample,
is selected in certain characteristics of the objects in a population. This
characteristics whose value may change from one object to another in the
population is called variable. A variable is discrete if its set of possible values
either is finite or else can be listed in an infinite sequence. A variable is
continuous if its possible values consist of an entire interval on the number
line.
In a probability problem, properties of population under study are assumed known,
and questions regarding a sample taken from the population are posed and answered.
In a statistics problem, characteristics of a sample are available to the experimenter,
and this information enables the experimenter to draw conclusions about the
populations.