# Random Variable

A set of numerical values assigned to the all possible outcomes of the random experiment are called random variable. The random variable can be briefly written as r.v. If we write **A, B,…, F** on the six faces of a die, these letters are not a r.v. If we write some numerical values on the six faces of a die like **I, 2, 3,…, 6**, we have a set of values called r.v. Suppose we select two bulbs from a certain lot having good and defective bulbs. Let **G** stand for good and **D** stand for defective. There are four possible outcomes which are **GG, GD, DG** and **DD**. Each outcome can be assigned some numerical value. Let us count number of defective bulbs in each outcome. We can write

Outcome |
No. of Defective Bulbs |

GG |
0 |

GD |
1 |

DG |
1 |

DD |
2 |

Thus the numerical values **0, 1, 2** are the values of the random variable where random variable is the number of defective bulbs in this discussion. A random variable is denoted by a capital letter . Here is the number of defective bulbs. The small letters are used for the specific values of the random variable. A random variable is also called chance variable. If we have two or more than two random variables we can use the letters for them. A random variable may be discrete or continuous.