Originally Posted by

**psgame_freak** Im confused with the formulas VAR[f(x)] = a^2VAR(X + b) and Sum of Independent Random VAR(C) = VAR(A) + VAR(B)

-Adult males of a certain species of animal are known to have a mean weight of 1.3 kg with standard error of .2 kg.

Q: What is the standard error of the total weight of randomly selected groups of 4 males?

Now I have 2 solutions with different answers.

Using VAR[f(x)] = a^2VAR(X + b)

= 4^2 (.2^2)

= 0.64 kg

hence Standard error is 0.8 kg

Using VAR(C) = VAR(A) + VAR(B)

= .2^2 + .2^2 + .2^2 + .2^2

= 0.16 kg

hence Standard error is 0.4 kg

Which one is right?

If its not much to ask, could you give me a link to help me with this?

How do we choose the constant?