150 likes | 171 Views
Chapter 12 Probability and Calculus. Chapter Outline. Discrete Random Variables Continuous Random Variables Expected Value and Variance Exponential and Normal Random Variables Poisson and Geometric Random Variables. § 12.1. Discrete Random Variables. Section Outline. Mean Expected Value
E N D
Chapter Outline • Discrete Random Variables • Continuous Random Variables • Expected Value and Variance • Exponential and Normal Random Variables • Poisson and Geometric Random Variables
§12.1 Discrete Random Variables
Section Outline • Mean • Expected Value • Variance • Standard Deviation • Frequency Table • Relative Frequency Table • Relative Frequency Histogram • Random Variable • Applications of Expected Value, Variance, and Standard Deviation
Expected Value • a1 is the first number from a set of numbers, a2 is the second and so on • p1 is the probability that a1 occurs, p2 is the probability that a2 occurs and so on
Variance • m is the expected value (or mean) of the set of numbers • a1 is the first number from a set of numbers, a2 is the second and so on • p1 is the probability that a1 occurs, p2 is the probability that a2 occurs and so on
Applications of Expected Value, Variance, & Standard Deviation EXAMPLE Find E(X), Var (X), and the standard deviation of X, where X is the random variable whose probability table is given in Table 5. SOLUTION
Applications of Expected Value EXAMPLE The number of phone calls coming into a telephone switchboard during each minute was recorded during an entire hour. During 30 of the 1-minute intervals there were no calls, during 20 intervals there was one call, and during 10 intervals there were two calls. A 1-minute interval is to be selected at random and the number of calls noted. Let X be the outcome. Then X is a random variable taking on the values 0, 1, and 2. (a) Write out a probability table for X. (b) Compute E(X). (c) Interpret E(X). SOLUTION (a)
Applications of Expected Value CONTINUED (b) (c) Since E(X) = 0.67, this means that the expected number of phone calls in a 1-minute period is 0.67 phone calls.