Other forms: educated guesses
If you don't know the answer to a question, but you're fairly knowledgeable about the subject, you can make an educated guess. This speculation, based on good information and clear reasoning, is often correct!
An educated guess is just what it sounds like: a guess that's not random, but based on previous education or knowledge of a topic. If you know a lot about different dog breeds, you may be able to make an educated guess about your friend's rescue pup: "My educated guess is that he's got some Akita in him, because of his black tongue and that curly tail."