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Learn how to construct a binomial probability distribution and apply the binomial probability formula for experiments involving Bernoulli trials. Understand the concept of success and failure and calculate the probability of specific outcomes.
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Chapter 11 Probability
Chapter 11: Probability • 11.1 Basic Concepts • 11.2 Events Involving “Not” and “Or” • 11.3 Conditional Probability and Events Involving “And” • 11.4 Binomial Probability • 11.5 Expected Value and Simulation
Section 11-4 • Binomial Probability
Binomial Probability • Construct a simple binomial probability distribution. • Apply the binomial probability formula for an experiment involving Bernoulli trials.
Binomial Probability Distribution p.617 The spinner below is spun twice and we are interested in the number of times a 2 is obtained (assume each sector is equally likely). Think of outcome 2 as a “success” and outcomes 1 and 3 as “failures.” The sample space is 2 1 3 S = {(1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3, 3)}.
Binomial Probability Distribution p.617 When the outcomes of an experiment are divided into just two categories, success and failure, the associated probabilities are called “binomial.” Repeated trials of the experiment, where the probability of success remains constant throughout all repetitions, are also known as Bernoulli trials.
Binomial Probability Distribution p.618 If x denotes the number of 2s occurring on each pair of spins, then x is an example of a random variable. In S, the number of 2s is 0 in four cases, 1 in four cases, and 2 in one case. Because the table on the next slide includes all the possible values of x and their probabilities, it is an example of a probability distribution. In this case, it is a binomial probability distribution.
Probability Distribution for the Number of 2s in Two Spins p.618
Binomial Probability Formula p.619-620 In general, let n = the number of repeated trials, p = the probability of success on any given trial, q = 1 – p = the probability of failure on any given trial, and x = the number of successes that occur. Note that p remains fixed throughout all n trials. This means that all trials are independent. In general, x successes can be assigned among n repeated trials in nCxdifferent ways.
Binomial Probability Formula p.620 When n independent repeated trials occur, where p = probability of success and q = probability of failure with p and q (where q = 1 – p) remaining constant throughout all n trials, the probability of exactly x successes is given by
Example: Finding Probability in Coin Tossing p.620 Find the probability of obtaining exactly three heads in five tosses of a fair coin. Solution This is a binomial experiment with n = 5, p = 1/2, q = 1/2, and x = 3.
Example: Finding Probability in Dice Rolling p.620 Find the probability of obtaining exactly two 3’s in six rolls of a fair die. Solution This is a binomial experiment with n = 6, p = 1/6, q = 5/6, and x = 2.
Example: Finding Probability in Dice Rolling Find the probability of obtaining less than two 3’s in six rolls of a fair die. Solution We have n = 6, p = 1/6, q = 5/6, and x < 2.
Example: Finding the Probability of Hits in Baseball p.621 A baseball player has a well-established batting average of 0.250. In the next series he will bat 10 times. Find the probability that he will get more than two hits. * challenging Solution In this case n = 10, p = 0.250, q = 0.750, and x > 2.
Example: Finding the Probability of Hits in Baseball Solution(continued)