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AP STATISTICS LESSON 8 - 1. THE BINOMIAL DISTRIBUTION. ESSENTIAL QUESTION: What is a binomial setting and how can binomial distributions be solved?. Objectives: To identify binomial settings. To become familiar with the binomial formula. To solve problems using the binomial formula.
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AP STATISTICSLESSON 8 - 1 THE BINOMIAL DISTRIBUTION
ESSENTIAL QUESTION: What is a binomial setting and how can binomial distributions be solved? Objectives: • To identify binomial settings. • To become familiar with the binomial formula. • To solve problems using the binomial formula.
Introduction In practice, we frequently encounter experimental situations where there are two outcomes of interest. Some examples are: • We use a coin toss to answer a question. • A basketball player shoots a free throw. • A young couple prepares for their first child.
The Binomial Setting • Each observation falls into one of just two categories, which for convenience we call “success” or “failure.” • There is a fixed number n of observations. • The n observations are all independent. (That is, knowing the results of one observation tells you nothing about the other observations). • The probability of success, call it p, is the same for each observation.
Binomial Distribution The distribution of the count X of successes in the binomial settings is the binomial distribution with parameters n and p. The parameter n is the number of observations, and p is the probability of a success on any one observation. The possible values of X are the whole numbers from 0 to n. As an abbreviation, we say that X is B(n,p).
Example 8.1Blood Typespage 440 Blood type is inherited. If both parents carry genes for the O and A blood types, each child has probability of 0.25 of getting two O genes and so of having blood type O. Different children inherit independently of each other. Find n, p and X.
Example 8.2page 440 Deal 10 cards from a shuffled deck and count the number X of red cards. There are 10 observations and each are either a red or a black card. Is this a binomial distribution? If so what are the variables n,p and X?
Example 8.3page 440 An engineer chooses an SRS of 10 switches from a shipment of 10,000 switches Suppose that (unknown to the engineer) 10% of the switches in the shipment are bad. The engineer counts the number X of bad switches in the sample. Is this a binomial situation? Why?
pdf Given a discrete random variable X, the probability distribution function assigns a probability to each value of X. The probability must satisfy the rules for probabilities given in Chapter 6.
Example 8.6page 443 Corinne is a basketball player who makes 75% of her free throws over the course of a season. In a key game, Corinne shoots 12 free throws and makes only 7 of them. The fans think that she failed because she is nervous. Is it unusual for Corinne to perform this poorly?
Example 8.7page 443 We want to determine the probability that all 3 children in a family are girls. Find n, p, and X.
cdf The cumulative binomial probability is useful in a situation of a range of probabilities. Given a random variable X, the cumulative distribution function (cdf) of X calculates the sum of the probabilities for 0,1,2,…, up to the value X. That is , it calculates the probability of obtaining a most X successes in n trials.
Example 8.8page 444 If Corrine shoots n = 12 free throws and makes no more than 7 of them?