Distinguish between (a) Continuous and (b) Discrete variables.

Continuous Variables : It can take all conceivable values in the given range. For example, heights and weights of individuals, prices of commodities, income of individuals may be treated as continuous variables. Although, in practice, the measurements are taken only approximately, upto one or two places of decimal, the true values may be anything in a certain range.
Discrete Variables : If the variables can taken only some particular value (like whole numbers), it is called a 'discrete' or 'discontinuous' variable. For example, number of students in different classes, different schools, or the size of households are discrete variables, as they can take interval values only.