Definitions

The letter x is typically used to denote a random variable. The following are examples of random variables.

x = The number of art majors in a statistics class

x = The number of men among 20 newly hired employees

x = The number of heads in four tosses of a coin

x = The number of diamonds in a hand of 5 cards

x = The weight of a randomly selected student

x = The income of a randomly selected shopper in a mall.

A random variable is called a discrete random variable if it has a finite or countable number of values. The first four examples or random variables given above are discrete.

A random variable is called a continuous random variable if it has infinitely many values. These involve measurements on a continuous scale that has no gaps.