hi there, im stuck on this question:

x 1 2 3 4

P(X=x) 0.1 0.2 0.4 0.3

the table shows the distribution of the discrete random variable X, find

(a) Var(X)

(b) Var(X^2)

(c) Var(24x^-1)

can sum1 please help me, i got exam on wednesday, thanxzz

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- Jan 18th 2010, 08:59 AMtejuStatistics for A2 students
hi there, im stuck on this question:

x 1 2 3 4

P(X=x) 0.1 0.2 0.4 0.3

the table shows the distribution of the discrete random variable X, find

(a) Var(X)

(b) Var(X^2)

(c) Var(24x^-1)

can sum1 please help me, i got exam on wednesday, thanxzz - Jan 18th 2010, 09:01 AMartvandalay11
do you know the formula for variance? and its easier counter part in terms of expected value... use that

then you need a theorem about variance when it comes to constants and random variables... are you familiar with that - Jan 18th 2010, 09:11 AMteju
- Jan 18th 2010, 01:30 PMmr fantastic
Construct a probability table for Y = X^2:

y 1 4 9 16

P(Y=y) 0.1 0.2 0.4 0.3

Now calculate Var(Y) just just like you calculated Var(X) in the first part.

Construct a probability table for W = 24x^-1 and calculate Var(W) just like you calculated Var(X) in the first part.