To assume is to come to a conclusion without knowing all the facts for certain or being sure that the information is correct, there is an old saying about this word, when you assume, you make an a.. Out of you to me
To make an assumption, is to make a judgment call on something or someone with little or no facts. There is an old expression, I don't know if they will let e say, but it breaks down the word to better understand its meaning. When you assume, you make an (first 3 letters) out of you (4th letter) to me (last 2 letters) an easy way to remember a general definition of the word
This is giving a good guess without any immediate thought.
Assumption is the same as null hypothesis