Statistics — Describing & Inferring
Describing data (mean, median, standard deviation), the normal curve and the 68–95–99.7 rule, and z-scores.
Statistics is probability run backwards: probability asks "given the rules, what will the data do?"; statistics asks "given the data, what are the rules?" It's how science separates a real effect from random noise.
- 01 Describing data — centre & spread ELI5: two numbers summarize a pile of data — where it centres and how spread out it is. mean = the balance point (average) median = the middle value (robust to…
- 02 The normal curve & the 68–95–99.7 rule ELI5: heap up enough independent measurements — heights, test scores, manufacturing errors — and they pile into the famous bell curve. The rule of thumb: about…
- 03 z-scores — how unusual is a value? ELI5: a z-score rescales any value into "how many standard deviations from the mean": z = (x − mean) / std. A z of 0 is dead average; z = 2 is…
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