Easiest practical way to assign a probability to a phrase based on a small corpus? • /r/MachineLearning

Hi all, I am looking for a practical and simple way to give a phrase a score based on the similarity to a corpus. For instance, let's say I have a small chat log as a corpus. Given two phrases "i am doing fine" and "car breaks tomorrow", the first sentence should have a higher score (or probability) than the second. I am interested in something easy to implement (or already implemented) solution, I m not doing research or trying to beat the state-of-the-art so deep learning and other complex solutions are probably not what I want.