# Initialisation methods and variance

I'm trying to understand some weights initialisation methods by reading the article http://proceedings.mlr.press/v9/glorot10a/glorot10a.pdf .

But I don't understand their notation on variance. Right in equation (5) they refer to a variable $$z^i$$ and I don't know what they mean by it: if it's a collective index for all examples or not?

• Please copy equation 5 and all related variable expansions to the question – Martin Thoma Dec 27 '18 at 6:49