The mathematics of uncertainty
Outcomes like "heads" or "the third red card" are awkward to do arithmetic with. A random variable fixes that: it's a rule that attaches a number to every outcome. Formally X: Ω → ℝ. Flip three coins and let X count the heads. Now each outcome maps to 0, 1, 2, or 3, and we can average, square, and sum.
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▶ Random Variables