Yes, "investigation" is a noun. It refers to the action of investigating or the process of carefully examining a situation or event in order to learn the truth about it.

make predictions

Added: Form hypotheses - make meticulous notes and carefully record all your stpes and the findings they produce.

Science is a systematic approach to acquiring knowledge through carefully documented investigation and experimentation.

It's purpose is to enable us to understand the universe in which we live.

Searchable means to make thorough examination of; look over carefully in order to find something or to explore. It is an act or searching to make a careful examination or investigation.

The correct term is "investigation of".