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Let X be a discrete random variable. The probability distribution of X is given below:

X 30 10 –10
P(X)


Then E(X) is equal to

  1. 6
  2. 4
  3. 3
  4. –5

Answer (Detailed Solution Below)

Option 2 : 4

Detailed Solution

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Concept:

The expectation of a random variable E(X) is given by 

Calculation:

Given:

X 30 10 –10
P(X)

Expectation E(X) is calculated by 

⇒ E(X) = 30 ×  + 10 ×  +( - 10)×  

⇒ E(X) = 6 + 3 - 5

⇒ E(X) = 4

∴ E(X) is equal to 4.

The correct answer is option 2.

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