The Condition Names the Denominator

A probability is a part over the right whole, so the condition names the denominator: fix the world first, then count inside it. AND multiplies, OR adds, at-least-one flips to one minus none, and without replacement the pool shrinks. Points leak in taking the conditional over the wrong group, combining with the wrong operation, and reporting a look-alike instead of the probability.

8 STEPS · 6 QUICK CHECKS · the condition sets the denominator · v1