# CBSE Class 12-science Answered

**Define variance and standard deviation of a random variable.**

Asked by Topperlearning User | 04 Jun, 2014, 01:23: PM

Expert Answer

** Variance of a Random Variable: **Let X be a random variable whose possible values x

_{1}, x

_{2}, x

_{3}, ..., x

_{n}occur with probabilities p

_{1}, p

_{2}, p

_{3},..., p

_{n}, respectively. Also,

_{}be the mean of X. The variance of X, denoted by Var (X) is defined as

_{}

__Standard Deviation of a Random Variable__**:**The non-negative number

_{};

_{}is called the standard deviation of random variable X.

Answered by | 04 Jun, 2014, 03:23: PM

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