OLS regression — the line that assumes it caused something
Least-squares regression is the workhorse everyone reaches for first; the danger is that a fitted coefficient reads like a cause when it is only a correlation under stated assumptions.
Not yet scoped.
Why
The point is not the fit but the assumptions behind it — linearity, independent errors, no omitted variable — and the PoC would show the same dataset giving opposite conclusions when one assumption is quietly violated.