Hi I have a question in regards to the stereoselectivity in wittig reactions.

Hi

I have a question in regards to the stereoselectivity in wittig reactions. Would you please tell me which of these 3 benzaldehyde derivatives (p-anisaldehyde, 4-nitrobenzaldehyde, & 4-hydroxybenzaldehyde) will have the highest E:Z ratio in alkene products and which will have the least? I know for a fact that it has to do with there electronegativity however I do not know why exactly.

Thanks in advance!