What is the best definition for educational psychology?what are the purpose, functions and importance of educational psychology?

Educational Psych is the science that studies patterns in
learning acquisition throughout human development in order to help predict and consider
the best developmentally-appropriate instructional methods that would help growing human
beings acquire information at the rate, pace, and volume that they need to get
it.

A person who studies Educational Psych as a major or
Masters in college will likely end up as a tester, that is, as a professional whose main
job is to determine the level of developmental appropriateness of a student who is
showing difficulty learning. It is quite cool and very quantitative. It is very
interesting, though.

However, Ed Psych is also rich and
valuable with qualitative data, because it shows whether the job of teachers is
effective in the learning process of specific students, or
not.

It is one of the most marvelous fields and I respect
it a lot.