"E" stands for "Electromotive force", which is essentially just voltage. We just have come used to using "V" instead of "E" It would be the same as asking why Current is "I" even though it is measured as Amps.
Single-blind of study is a type of research procedure in which the researcher is the only one that knows the experimental and control group, only the researcher knows the treatment each group is receiving. The aim of this method is to reduce bias in the study.
