A Discrete variable is countable in a finite amount of time while a Continous variable is uncountable in a finite amount of time.
Therefore, grouping the variables into Discrete and Continous, we have:
a) The fuel efficiency, in miles per gallon, of an American-made car >>> Continous variable.
b) The number of personal-injury traffic accidents last week on Interstate 65 in Indiana >>>Discrete variable.
c) In an experimental study, the participant's estimate for the height of a 3-meter image >>> Continous variable.
d) The highest grade level (1st, 2nd, or 3rd) completed by a high-school dropout >>> Discrete variable
