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Approximately \(75 \%\) of all marketing personnel are extroverts, whereas about \(60 \%\) of all computer programmers are introverts (Source: \(A\) Guide to the Development and Use of the Myers-Briggs Type Indicator, by Mycrs and McCaulley). (a) At a mecting of 15 marketing personnel, what is the probability that 10 or more are extroverts? What is the probability that 5 or more are extroverts? What is the probability that all are extroverts? (b) In a group of 5 computer programmers, what is the probability that none are introverts? What is the probability that 3 or more are introverts? What is the probability that all are introverts?

Short Answer

Expert verified
(a) Probability: 10 or more extroverts ≈ 0.854, 5 or more ≈ 0.999, all ≈ 0.013; (b) 0 introverts ≈ 0.010, 3 or more ≈ 0.682, all introverts ≈ 0.078.

Step by step solution

01

Understanding the Problem - Part (a)

In part (a), we are dealing with marketing personnel. We know that 75% of them are extroverts, and we want to find probabilities related to a meeting of 15 personnel. We are looking for specific probabilities of having 10 or more, 5 or more, and all extroverts in this group.
02

Setting Up Probability for Binomial Distribution - Part (a)

The probability of any one marketing person being an extrovert is \(p = 0.75\). We will use the binomial distribution where \(n = 15\) (number of trials) to find the probabilities for the required cases. The probability for \(X\) extroverts out of 15 is given by the binomial formula: \(P(X = x) = \binom{n}{x} p^x (1-p)^{n-x}\).
03

Calculating Probability that 10 or More are Extroverts

For \(X \geq 10\), we need \(P(10 \leq X \leq 15)\). This is \(P(X = 10) + P(X = 11) + \cdots + P(X = 15)\). Using the binomial formula, calculate each probability and sum them up.
04

Calculating Probability that 5 or More are Extroverts

For \(X \geq 5\), we want \(P(5 \leq X \leq 15)\). Similar to the previous step, use the binomial formula to compute \(P(X = 5), P(X = 6), \ldots, P(X = 15)\) and sum them up.
05

Calculating Probability that All are Extroverts

To find the probability that all 15 are extroverts, compute \(P(X = 15)\) using the binomial formula.
06

Understanding the Problem - Part (b)

In part (b), we are considering computer programmers. We know 60% are introverts. We are finding probabilities related to a group of 5 programmers, specifically those having none, 3 or more, and all introverts.
07

Setting Up Probability for Binomial Distribution - Part (b)

The probability of a programmer being an introvert is \(p = 0.6\). Use binomial distribution where \(n = 5\) to find the probabilities. The probability for \(Y\) introverts out of 5 is given by: \(P(Y = y) = \binom{n}{y} p^y (1-p)^{n-y}\).
08

Calculating Probability that None Are Introverts

For none (\(Y = 0\)), compute \(P(Y = 0)\) using the binomial formula.
09

Calculating Probability that 3 or More are Introverts

For \(Y \geq 3\), calculate \(P(3 \leq Y \leq 5)\). Find the probabilities \(P(Y = 3), P(Y = 4), P(Y = 5)\) and sum them up.
10

Calculating Probability that All are Introverts

For all being introverts (\(Y = 5\)), compute \(P(Y = 5)\) using the binomial formula.

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Key Concepts

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

Probability
Probability is a measure of how likely an event is to occur. In our exercise, it's all about determining how often certain outcomes happen when dealing with extroverts in marketing personnel and introverts in computer programmers. For example, we want to know the likelihood that a certain number, say 10 or more out of 15 marketing personnel, will be extroverts.

To achieve this, we calculate the probability using the concept of a binomial distribution, which helps us find the chances of a specific number of successes in a set number of trials.
  • Probability values can range between 0 (impossible event) and 1 (certain event).
  • In practical situations, we often look at percentages, like the 75% chance of an individual being an extrovert.
Understanding probability is critical to make sense of how likely an outcome is, which is a fundamental part of statistical problem-solving.
Extroverts and Introverts
Extroverts and introverts are personality types used to describe how people interact with the social world. Extroverts are typically outgoing, enjoy socializing, and often perform well in roles that require lots of interaction—like marketing. On the other hand, introverts tend to enjoy quieter activities and may prefer solitary work environments, which can often be found in programming.

In terms of probability, having 75% of marketing personnel being extroverts and 60% of computer programmers being introverts gives us a basis to make various predictions.
  • Understanding these traits helps us contextualize why certain probabilities are higher for certain professions.
  • This knowledge can be used for organizational planning and team-building strategies.
Thus, when solving statistics problems involving personalities, taking into account these traits helps in interpreting the results better.
Statistics Problem Solving
Statistics problem solving generally involves a series of steps to understand, analyze, and calculate probabilities for specific outcomes. In the problem you're solving, you need to:
  • Understand the given data and what is being asked—this could involve defining what it means for people to be extroverts or introverts.
  • Set up the distribution and determine the parameters you will use, like probability and number of trials.
  • Calculate the probabilities of different outcomes—like having 10 or more extroverts in a group of 15 using specific statistical formulas.
Throughout these tasks, being methodical is crucial. Understanding how to approach a problem systematically can make complex statistical concepts easier to handle.
Binomial Formula
The binomial formula is a powerful tool in probability and statistics, used particularly when you have a fixed number of identical trials or experiments, each with two possible outcomes: success or failure. In this exercise, we use it to determine the likelihood of different numbers of extroverts in marketing and introverts in computer programming scenarios.

The formula is: \[P(X = x) = \binom{n}{x} p^x (1-p)^{n-x}\] This formula allows us to calculate the probability (P(X = x)) of observing exactly X successes (or extroverts/introverts, in our context) in n trials, where each trial has a probability p of success.
  • "\(\binom{n}{x}\)" is the binomial coefficient, representing the number of ways to choose x successes from n trials.
  • "\(p^x\)" is the probability of x successes.
  • "\((1-p)^{n-x}\)" is the probability of n-x failures.
Using the binomial formula makes it possible to quickly calculate the chance of any particular scenario occurring, which is especially useful in predicting outcomes based on known probabilities.

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Most popular questions from this chapter

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?

Expand Your Knowledge: Multinomial Probability Distribution Consider a multinomial experiment. This means the following: 1\. The trials are independent and repeated under identical conditions. 2\. The outcomes of each trial falls into exactly one of \(k \geq 2\) categories. 3\. The probability that the outcomes of a single trial will fall into ith category is \(p_{i}\) (where \(i=1,2 \ldots, k\) ) and remains the same for each trial. Furthermore, \(p_{1}+p_{2}+\ldots+p_{k}=1\) 4\. Let \(r_{i}\) be a random variable that represents the number of trials in which the outcomes falls into category \(i\). If you have \(n\) trials, then \(r_{1}+r_{2}+\ldots\) \(+r_{k}=n .\) The multinational probability distribution is then $$P\left(r_{1}, r_{2}, \cdots r_{k}\right)=\frac{n !}{r_{1} ! r_{2} ! \cdots r_{2} !} p_{1}^{r_{1}} p_{2}^{(2)} \cdots p_{k}^{r_{2}}$$ How are the multinomial distribution and the binomial distribution related? For the special case \(k=2,\) we use the notation \(r_{1}=r, r_{2}=n-r, p_{1}=p\) and \(p_{2}=q .\) In this special case, the multinomial distribution becomes the binomial distribution. The city of Boulder, Colorado is having an election to determine the establishment of a new municipal electrical power plant. The new plant would emphasize renewable energy (e.g., wind, solar, geothermal). A recent large survey of Boulder voters showed \(50 \%\) favor the new plant, \(30 \%\) oppose it, and \(20 \%\) are undecided. Let \(p_{1}=0.5, p_{2}=0.3,\) and \(p_{3}=0.2 .\) Suppose a random sample of \(n=6\) Boulder voters is taken. What is the probability that (a) \(r_{1}=3\) favor, \(r_{2}=2\) oppose, and \(r_{3}=1\) are undecided regarding the new power plant? (b) \(r_{1}=4\) favor, \(r_{2}=2\) oppose, and \(r_{3}=0\) are undecided regarding the new power plant?

USA Today reported that the U.S. (annual) birthrate is about 16 per 1000 people, and the death rate is about 8 per 1000 people. (a) Explain why the Poisson probability distribution would be a good choice for the random variable \(r=\) number of births (or deaths) for a community of a given population size. (b) In a community of 1000 people, what is the (annual) probability of 10 births? What is the probability of 10 deaths? What is the probability of 16 births? 16 deaths? (c) Repeat part (b) for a community of 1500 people. You will need to use a calculator to compute \(P(10 \text { births) and } P(16\text { births). }\) (d) Repeat part (b) for a community of 750 people.

Jim is a real estate agent who sells large commercial buildings. Because his commission is so large on a single sale, he does not need to sell many buildings to make a good living. History shows that Jim has a record of selling an average of eight large commercial buildings every 275 days. (a) Explain why a Poisson probability distribution would be a good choice for \(r=\) number of buildings sold in a given time interval. (b) In a 60 -day period, what is the probability that Jim will make no sales? one sale? two or more sales? (c) In a 90 -day period, what is the probability that Jim will make no sales? two sales? three or more sales?

Innocent until proven guilty? In Japanese criminal trials, about \(95 \%\) of the defendants are found guilty. In the United States, about \(60 \%\) of the defendants are found guilty in criminal trials (Source: The Book of Risks, by Larry Laudan, John Wiley and Sons). Suppose you are a news reporter following seven criminal trials. (a) If the trials were in Japan, what is the probability that all the defendants would be found guilty? What is this probability if the trials were in the United States? (b) Of the seven trials, what is the expected number of guilty verdicts in Japan? What is the expected number in the United States? What is the standard deviation in each case? (c) As a U.S. news reporter, how many trials \(n\) would you need to cover to be at least \(99 \%\) sure of two or more convictions? How many trials \(n\) would you need if you covered trials in Japan?

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