Hi;

I know the formula is Z = (X - mean)/standard deviation,What I don't know

is how do I know when I convert a normal distribution into z

which is written as X ~ N(mean,variance or standard deviation).

How do I know if X ~ N(50,4) the number 4 is variance or standard deviation

because when I put it back into the Z formula it has to be divided by standard deviation?

Thanks.