# Thread: [SOLVED] Mean and sd of transformation

1. ## [SOLVED] Mean and sd of transformation

X is random variable with mean 44.584 and sd 89.265. What non zero value maust a take so that random variable given by Y=aX + a^2 has its mean equal to its sd?

I get 44.681 but am not sure if method is correct:

E(Y) = a*mean + a^2

V(Y) = a^2*sd^2

and then equate them.

Is this right?

2. Originally Posted by javs156
X is random variable with mean 44.584 and sd 89.265. What non zero value maust a take so that random variable given by Y=aX + a^2 has its mean equal to its sd?

I get 44.681 but am not sure if method is correct:

E(Y) = a*mean + a^2

V(Y) = a^2*sd^2

and then equate them.

Is this right?
Your method is correct (provided mean and sd^2 refer to the random variable X). I haven't checked the arithmetic.

3. would sum1 mind checking that the answer is correct?

4. Originally Posted by javs156
would sum1 mind checking that the answer is correct?
It's easier (for me anyway) to check an answer (as opposed to validating a method) if the details of the calculation leading to the answer are given. Please keep that in mind for next time.