Math 4030-3a Discrete Random Variables
Random variable A function that assigns a numerical value to each possible outcome in the sample space. One value for one outcome. i.e. different value must mean different outcomes. However, different outcomes may have the same value. Random variable may take discrete or continuous values. Sample space S R 5/28/2018
Probability Distribution of a discrete random variable: A list of probability values corresponding to all values of a discrete random variable X. i.e. for any value x that the random variable X takes. 5/28/2018
Probability histogram and bar chart; Cumulative distribution function F(x): If X takes values then 5/28/2018
Mean of a random variable Mean may or may not exist; Even exists, may or may not be a finite number; If X has only finitely many values, then mean exists and is a finite value. Average value Balance point Expect value 5/28/2018
Properties of Means: Linearity: Warning: 5/28/2018
Variance of a random variable Variance is a “mean”; Always nonnegative; Variance may or may not exist; Even exists, may or may not be a finite number; If X has only finitely many values, then variance exists and is a finite value. Measure the variability of X Spread of the histogram Un-predictable, risky, … 5/28/2018
Properties of variance Warning: 5/28/2018
Chebyshev’s Theorem If X is a random variable with mean and standard deviation , then for any number k > 1, Equivalently, 5/28/2018