What must be true for a research question to be considered effective?

two things to keep in mind when writing a research question would be:

it needs to be a "how' question, and not a why. ex. "How does the number of fish in a given area affect the population of insects in the ecosystem surrounding that area", not "why does the number of fish change the number of insects in an area", the why question is much too broad. it needs to be a bit specific editing our previous example, "How does the number of catfish (a specific kind of fish) affect the population of pond-skaters (specific insect) in the ecosystem surrounding the Mississippi River (specific place)."

This makes your research question much more clear and effective