The concept of Null Hypotheses can be confusing, because it is about nothingness. And the human mind is wired to understand things that exist, not things that don't exist.
I've found that it helps to state the Null Hypothesis as either
So, if we are comparing the Means of Populations A and B, we could say:
Null Hypothesis (H0) "There is no difference between the Mean of Population A and the Mean of Population B."
But, it can be stated even more clearly and succinctly as an equation:
And the Alternative Hypothesis would be the opposite of this:
This is for a 2-tailed test:
It gets more complicated when we get into 1-tailed tests. In those tests, we'd have either
But that would be the subject of another Statistics Tip.
Andrew A. (Andy) Jawlik is the author of the book, Statistics from A to Z -- Confusing Concepts Clarified, published by Wiley.