STAB22H3 Lecture Notes - Lecture 9: Probability Distribution, Squared Deviations From The Mean, Pcx
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STAB22H3 Full Course Notes
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a random variable (r. v. ) is a variable whose value is a numerical outcome of a random phenomenon. X = 1 if a h comes up. This is an example of a bernoulli r. v. P(x = x) q p p +q = 1. Each value of a random variable is an event, so each value has probability. List of values and probabilities called probability model. Mean not (2+3+4+5)/4=3. 5 because 4 and 5 more likely than 2 or 3. Have to account for more likely values when adding up: Median is value of x where summed-up probabilities first pass 0. 5: 3 too small (total 0. 1+0. 2=0. 3), 4 is right (0. 1+0. 2+0. 4=0. 7), so median 4. Mean a little smaller than median: left- skewed. the variance of a r. v. p425. The variance of a r. v. is an average of the squared deviations. Variance of a discrete r. v. is.
