Start with what the number can justify
Most statistical mistakes are not arithmetic errors. They are mismatches between a number and the claim built on it: a convenience sample used to describe a nation, a correlation presented as a cause, a single p-value treated as proof. So every lesson opens by asking what the result could support, and then works through the reasoning.
Our writing rules
- Example before formula. You meet the situation first; notation arrives when it saves words.
- Every symbol read aloud. The first time "|" or "Σ" appears, we say what it means in English.
- Assumptions named. Each worked example lists what has to be true for the answer to hold.
- Estimate versus conclusion. We separate a useful working number from a claim you could defend.
- Hypothetical data labeled. Invented numbers used for teaching are marked as such; photographs are illustrations, never evidence.