ECON2209 Lecture 6: 3February_EconStats_Karagodsky
Document Summary
A random variable is a space or series of possible outcomes. P (x = x1) : the probability that the random variable is equal to this speci c outcome. Discrete: the outcomes are one or the other but not in between. 2. 1 expected value (or mean) of a discrete random var. k. P (x = xi)xi ex: years at bc, compute expected value of x: E[x] = . 3 1 + . 25 2 + . 2 3 + . 25 4 = 2. 4. 2. 3 standard deviation of a discrete random variable x. P (x)(x )2 = 3. (1. 96) + . 25(. 16) + . 2(. 36) + . 25(2. 56) = 1. 34. 4 properties of join probability distributions x y. P (x = 2| y = 7) = . 1. E[x] = 4. 3 = . 35(2) + . 15(4) + . 5(6) E [x| y = 7) = 4. 75 = . 25(2) + . 125(4) + . 625(6) var(x) = . 25( 2. 3)2 + . 15( . 3)2 + . 5(1. 7)2.
