Variables that can only take on a finite number of values are
called "discrete variables." All qualitative
variables are discrete. Some quantitative
variables are discrete, such as performance rated as 1,2,3,4, or 5, or temperature
rounded to the nearest degree. Sometimes, a variable that takes on enough discrete
values can be considered to be continuous for practical purposes. One example
is time to the nearest millisecond.
Variables that can take on an infinite number of possible values are called "continuous variables."