Day 11 Instructor-Led Video — Rule Era Boundaries

Core Claim

Rule changes create hard analytical boundaries that must split history.

Why It Matters

This is where a familiar label can hide a different rule. Rule changes create hard analytical boundaries that must split history. When the matrix is named first, the answer stays fair. When it is skipped, the claim sounds cleaner than it is.

Practical Takeaway

Before answering any family-spanning question, write one line that states matrix type, object type, and primary metric.

Common Misread

Comparing across a rule change as if nothing changed.