index cbc988b..36b2cfd 100644
@@ -22,6 +22,8 @@ measurement theorists classify scales:
- **interval**: temperature. equal differences are meaningful, but ratios aren't.
- **ratio**: weight, length, time. has a true zero. ratios are meaningful.
+these scale types are really a classification problem — [[structural/set-theory-as-thinking|set theory]] in disguise. each scale type defines a category with specific rules about what operations are valid.
+
every time someone averages ordinal data ("our average customer rating is 3.7 stars"), they're making a measurement theory error that we've all collectively agreed to ignore.
## precision vs accuracy
@@ -42,4 +44,4 @@ the mars climate orbiter crashed because one team used metric and another used i
counting and measurement aren't just "basic math" — they're the interface between abstract numbers and physical reality. every measurement is a tiny philosophical act: you're claiming that some aspect of the messy, continuous, complicated world can be captured by a number. that claim is always an approximation, always a choice, and understanding the nature of that approximation is where the real math begins.
-this connects directly to [calculus as thinking](/wiki/structural/calculus-as-thinking) — the question of "how precisely can we measure change?" is what led newton and leibniz to invent calculus. and [estimation](/wiki/immediate/patterns-and-estimation) is the practical skill of knowing when high precision matters and when it doesn't.
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+this connects directly to [calculus as thinking](/wiki/structural/calculus-as-thinking) — the question of "how precisely can we measure change?" is what led newton and leibniz to invent calculus. and [estimation](/wiki/immediate/patterns-and-estimation) is the practical skill of knowing when high precision matters and when it doesn't. measurement also connects to [[immediate/ordering-and-comparison|ordering]] — once you can measure things, you can rank them, but the type of measurement determines what kind of ordering is valid.
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