What is
the inference of Matthew makes a snowball​

Snowball sampling is where research participants recruit other participants for a test or study. It is used where potential participants are hard to find. It’s called snowball sampling because (in theory) once you have the ball rolling, it picks up more “snow” along the way and becomes larger and larger. Snowball sampling is a non-probability sampling method. It doesn’t have the probability involved, with say, simple random sampling (where the odds are the same for any particular participant being chosen). Rather, the researchers used their own judgment to choose participants.