a person who studies people but not an psychologist
caladarian
a mathematician
A cardiologist.
Properties
Your question is a bit difficult to understand. Perhaps you mean to ask: Question: What do you call someone who studies the statistics related to human populations? Answer: A demographer. http://en.wikipedia.org/wiki/Demographics
A statistician
You call someone that studies metal a metallurgist.
A scientist who studies the growth and density of populations and their vital statistics is known as a demographist!
A student. A statistician is perhaps the word you are looking for, but people in many other disciplines study statistics.
A physicist.
a person who studies planets is a planetologist.
There is no special name for someone who studies Hebrew.
A numismatist.
A Zoologist
An Anthropologist.
malacologist