Calculator Homework #2 - Probabilities for Discrete Random Variables To find the probability for a binomial variable: Example: Exactly x = 3 successes in n = 6 trials with probability of success p = 0.18 1. Press 2nd [DISTR] then [ALPHA][A] to get binompdf(. 2. Enter 6, .18, 3) then press ENTER. Display: .0643115635 Example: At most x = 4 successes in n = 10 trials with probability of success p = .12 1. Press 2nd [DISTR] then [ALPHA][B] to get binomcdf(. 2. Enter 10, .12, 4) then press ENTER. Display: .9962839325 Example: At least x = 4 successes in n = 12 trials with probability of success p = .08 (At least 4 is the complement of 3 or fewer) 1. Press 1 then - (minus) on the home screen 2 nd [DISTR] [ALPHA][B] to get binomcdf(. 2. Enter 12, .08, 3) To find the probability for a Poisson variable: Example: = 2, x = 3 1. Press 2nd [DISTR] then [ALPHA][C] to get poissonpdf(. 2. Enter 2, 3) Display: .1804470443 To find the probability for a geometric variable: Example: p = .14, x = 5 1. Press 2nd [DISTR] then [ALPHA][E] to get geometpdf(. 2. Enter .14, 5) Display: .0765811424 Exercise 1 A survey indicates that among college females 35% of them say shopping is their favorite pastime. Suppose that you randomly select 5 females on your campus. a. What is the probability that exactly 2 of them say shopping is their favorite pastime? b. What is the probability that at most 4 of them say shopping is their favorite pastime? c. What is the probability that at least 4 of them say shopping is their favorite pastime? Exercise 2 IHOP is so popular that they boast to sell a stack of pancakes every 2 minutes. What is the probability that there is a 10-minute interval in which no pancakes are sold? (The mean number of stacks for 10 minutes = 5) Exercise 3 To start his old mower, Tom has to pull a cord and hope for some luck. On any particular pull, the mower has a 10% chance of starting. Find the probability that it takes him exactly 3 pulls to start the mower