Why would you choose one type of observation over another when tracking children's behavior and skills?

In other kinds of situations, but in a more complex situation, it is better to make multiple observations in order to obtain a proper analysis on the child’s behavior, I hope this somewhat helps!

Paranoid schizophrenia i believe

That's  a project for you to do. btw your teacher probably uses a plagiarism detector and if you do copy anything on this site she/ he will find out and instead of getting a good  or bad grade you'll  get a 0 no exceptions, and they'll  probably call ur parents. so do some research ask friends and fam to you.