Normalization (z-transform) formula?
I am a bit confused what the true formula for z-transform normalization in rapidminer is, normally it is (X-arithmeticMean(X))/std.deviation
but what is the standard-deviation formula? one like that:
or one used in studentizing:
or sample variance?
and what do I use if I don't know the real arithmetic mean of my values X or the probability distribution of my values of X ?
because variance uses Expectation values from X, and its variance = SUM(p(x)*X)