Problem  Back to Problems Page 
A random variable x takes the values of &m inus;1, 0, 1. Its mean is 0.6.
If P(X = 0) = 0.2, then P(X = 1) = ? Net Answers :

Solution  
"x" represent the value in the range of the random variable "X".
P(X = 0) = 0.2 ⇒ f(0) = 0.2 Let P(X = − 1) = "a" and P(X = 1) = "b" Since f(x) represents the probability mass function, the discrete probability distribution of "x" would be
Since f(x) is a probability mass function,
Calculations for Mean and Standard Deviations
Expectation/Mean of the distribution
Solving (1) and (2) we get,
Substituting the value of "b" in (1) we get, a + b = 0.8 ⇒ a + 0.7 = 0.8 ⇒ a = 0.8 − 0.7 ⇒ a = 0.1 The distribution with the values of "a" and "b" replaced would be
Therefore, P(x=1) = b ⇒ P(x=1) = 0.7 Variance of the distribution

Credit : Vijayalakshmi Desu 