PENGUIN DICTIONARY OF STATISTICS, THE

A random variable that can take only two possible values. For example, the result of a driving test is a pass or a fail, and the outcome of a toss of a coin may be 'heads' or 'tails'. Such binary variables can be represented by a variable X that takes only the values 0 and 1. Thus, in a study of test results, we might assign X = 0 to a failure and X = 1 to a pass.

Frequency curve:

A smooth curve approximating a frequency polygon for a large set of observations which have been grouped using small class intetrvals. The term is also used for the graph of the frequency function of a continuous variable