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Basic Computation: Binomial Distribution Consider a binomial experiment with \(n=7\) trials where the probability of success on a single trial is \(p=0.60\). (a) Find \(P(r=7)\). (b) Find \(P(r \leq 6)\) by using the complement rule.

Short Answer

Expert verified
(a) \(P(r=7) \approx 0.028\); (b) \(P(r \leq 6) \approx 0.972\).

Step by step solution

01

Understand the Problem

We are dealing with a binomial distribution, defined by two parameters: the number of trials, \(n = 7\), and the probability of success on each trial, \(p = 0.60\). We need to find the probability of exactly 7 successes \(P(r=7)\) and the probability of having at most 6 successes \(P(r \leq 6)\).
02

Use the Binomial Formula for P(r=7)

The probability of exactly \(r\) successes is given by the binomial formula: \(P(r) = \binom{n}{r} p^r (1-p)^{n-r}\). For \(r=7\), this becomes \(P(r=7) = \binom{7}{7} (0.60)^7 (1-0.60)^{0}\).
03

Compute P(r=7)

\(\binom{7}{7} = 1\) since there is only one way to choose all successes in 7 trials. So we calculate \((0.60)^7\): \[ P(r=7) = 1 \times (0.60)^7 \times (0.40)^0 = (0.60)^7 \approx 0.02799 \].
04

Use Complement Rule for P(r ≤ 6)

The probability \(P(r \leq 6)\) can be found using the complement rule: \(P(r \leq 6) = 1 - P(r > 6) = 1 - P(r=7)\).
05

Compute P(r ≤ 6)

We already found \(P(r=7)\) in Step 3. So, \[ P(r \leq 6) = 1 - 0.02799 = 0.97201 \].

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Probability Theory
Probability theory is a branch of mathematics that deals with calculating the likelihood of different outcomes. In our exercise, we assess a scenario modeled by a binomial distribution. This distribution helps calculate the probability of achieving a fixed number of successes in a series of independent and identically distributed trials. In each trial, there are only two possible outcomes: success or failure. This aligns with common probability scenarios like flipping a coin or rolling a dice.
In our specific case, we have a binomial experiment with 7 trials, and each trial has a probability of success of 0.60. This forms the base of our calculation. Probability theory not only helps in determining these probabilities but also provides methods like the binomial formula to make exact calculations.
  • The binomial formula used is: \(P(r) = \binom{n}{r} p^r (1-p)^{n-r}\).
  • In the problem, 'r' denotes the number of successful outcomes we want to assess the probability for.
By using these formulas, we can determine the probability of any specific number of successes occurring in our trials.
Complement Rule
The complement rule is a useful concept in probability theory. It helps find the probability of an event not occurring by subtracting the probability of the event occurring from 1. In mathematical terms, it's often expressed as \(P( ext{not A}) = 1 - P( ext{A})\).
This rule is particularly handy for large computations as it simplifies the problem. For example, instead of summing several probabilities, we can sometimes subtract one probability from one and find the result more straightforwardly.
In our binomial distribution exercise, the problem asks for the probability of having at most 6 successes \(P(r \leq 6)\). Calculating this directly might involve finding the probability of 0 through 6 successes. However, using the complement rule simplifies this to \(P(r \leq 6) = 1 - P(r > 6)\), which equates to \(1 - P(r = 7)\) since it is a 7-trial experiment. Thus, we utilize what's already computed, \(P(r = 7)\), and subtract it from one to get the solution.
Statistical Distribution
Statistical distributions describe how probabilities are assigned to different outcomes of a random variable. In our problem, we focus on the binomial distribution, which is characterized by two parameters: the number of trials (\(n\)) and the probability of success in each trial (\(p\)).
The binomial distribution is a discrete distribution, meaning it deals with discrete variables and finite outcomes. It can be visualized as a series of bars representing the probability of each number of successes from 0 to \(n\).
This distribution is a cornerstone in statistics due to its ability to model numerous real-life situations where outcomes follow a "success/failure" type of scenario:
  • It helps quantify phenomena like the number of heads when flipping a coin multiple times.
  • In our case, it models an experiment with 7 trials, each with a probability of 0.60 of succeeding.
Understanding statistical distributions, especially the binomial distribution, is crucial in predicting and estimating various results of practical occurrences.

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Most popular questions from this chapter

Sociology: Dress Habits A research team at Cornell University conducted a study showing that approximately \(10 \%\) of all businessmen who wear ties wear them so tightly that they actually reduce blood flow to the brain, diminishing cerebral functions (Source: Chances: Risk and Odds in Everyday Life, by James Burke). At a board meeting of 20 businessmen, all of whom wear ties, what is the probability that (a) at least one tie is too tight? (b) more than two ties are too tight? (c) no tie is too tight? (d) at least 18 ties are not too tight?

Statistical Literacy What does it mean to say that the trials of an experiment are independent?

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Archaeology: Artifacts At Burnt Mesa Pueblo, in one of the archaeological excavation sites, the artifact density (number of prehistoric artifacts per 10 liters of sediment) was \(1.5\) (Source: Bandelier Archaeological Excavation Project: Summer 1990 Excavations at Burnt Mesa Pueblo and Casa del Rito, edited by Kohler, Washington State University Department of Anthropology). Suppose you are going to dig up and examine 50 liters of sediment at this site. Let \(r=0,1,2,3, \ldots\) be a random variable that represents the number of prehistoric artifacts found in your 50 liters of sediment. (a) Explain why the Poisson distribution would be a good choice for the probability distribution of \(r\). What is \(\lambda ?\) Write out the formula for the probability distribution of the random variable \(r\). (b) Compute the probabilities that in your 50 liters of sediment you will find two prehistoric artifacts, three prehistoric artifacts, and four prehistoric artifacts. (c) Find the probability that you will find three or more prehistoric artifacts in the 50 liters of sediment. (d) Find the probability that you will find fewer than three prehistoric artifacts in the 50 liters of sediment.

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