हिंदी

Probability Distribution of Discrete Random Variables - Expected Value and Variance of a Random Variable

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Topics

Estimated time: 4 minutes
  • Apply arithmetic mean of frequency distribution to find the expected value of a random variable 
  • Calculate the Variance and S.D. of a random variable
Maharashtra State Board: Class 12

Definition: Expected Value

If a discrete random variable X has possible values x₁, x₂, …, xₙ with corresponding probabilities p₁, p₂, …, pₙ, then the expected value E(X) is defined as

E(X) = x₁p₁ + x₂p₂ + … + xₙpₙ = Σ xᵢpᵢ

E(X) is also called the mean, which is denoted by μ.

Maharashtra State Board: Class 12

Formula: Expected Value

E(X) = Σxᵢpᵢ

Maharashtra State Board: Class 12

Formula: Variance

Var = E(X²) − [E(X)]²

Maharashtra State Board: Class 12

Formula: Standard Deviation

\[\mathrm{SD}(X)=\sqrt{E(X^{2})-\left[E(X)\right]^{2}}\]

SD = √Var

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