David Marks Staff asked 4 years ago

# What is the standard deviation ? of X

#### What is the standard deviation ? of X for the probability distribution?

The answer must be rounded to two decimal places. This is what I got – ? = Incorrect: Your answer is incorrect. . x 1 2 3 4 P(X = x) 0.3 0.5 0.1 0.1

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David Marks Staff answered 4 years ago

Var(X) = E(X-?)^2
From the given values,
?= Px
= 1(0.3) +2(0.5)+3(0.1) + 4(0.1)
= 0.3+1+0.3+0.4
=2
Var(X) = E(X-?)^2
=(1-2)^2 (0.3)+(2-2)^2(0.5) + (3-2)^2(0.1) + (4-2)^2(0.1)
= 0.3 + 0 + 0.1 +0.4
= 0.8

Standard deviation, ? = ? Var(X)
= ? 0.8
= 0.894427191
=0.89