You've forgotten the question. You've strayed. Go back to the original question I asked and talk about specific and direct data that allows us to know the original stateent is true.
How do you know it is not uniform?
I just did.
You want to know how we know. Metaphysics.
Before you examine the data, you decide on a degree of confidence that will convince you.
You collect your data, or plot data that was independently collected. You write an equation based on a theory. You draw a line through the data based on that equation. It matches. The conclusion: the theory that draws the line explains the data.
You check that level of agreement using statistics. It matches to that level of confidence.
You write a paper. You present it. You get questions from your peers. You answer them, or you identify where additional work is needed, either to the theory, or to the data.