# Standard deviation Formula

Hi All,

I am confused on when use the general formula to calculate St deviation and when basically compute it by inputting the weights.

I will put two examples of the Exam 1 of Kaplan Schweser:

In Q6A the standard deviation of the portfolio is calculated using its formula and assuming the correlation is 0 (squaring the numbers, adding them and then doing the root) But in a similar problem, in Q9B, the standard deviation is calculated simply using their weights and adding them together. Why? I do understand in which situations we have to use the formula or simply using the weights as in 9b… Could you please clarify? Thank you

S

Simply using the weights is just approximation, therefore may be overstated. However, Schweser says it may be used if correlation among the assets is 1.

Would you use the full calculation in the exam or the normal weighting?

if you look at the Schweser online assessments it uses weightings?

Would you use the full calculation in the exam or the normal weighting?

if you look at the Schweser online assessments it uses weightings?

It confusing… I still don’t know in what cases uses one or another.