Complete question :
The expected value of a random variable X is 140 and the standard deviation is 14. The standard deviation of the random variable Y=3X-10 is:
Answer:
42
Step-by-step explanation:
Standard deviation of Y = 3X - 10
The variance of Y
Var(Y) = Var(3X - 10)
Var(Y) = Var(3X) - Var(10)
10 is a constant :
Var(10) = 0
Hence,
Var(Y) = Var(3x)
SD(Y) = Var(Y) = Var(3X)
SD(Y) = SD(3X)
SD(Y) = 3SD(X)
SD(X) = 14
SD(Y) = 3 * 14
SD(Y) = 42
