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The Census Bureau's Current Population Survey shows \(28 \%\) of individuals, ages 25 and older, have completed four years of college (The New York Times Almanac, 2006). For a sample of 15 individuals, ages 25 and older, answer the following questions: a. What is the probability four will have completed four years of college? b. What is the probability three or more will have completed four years of college?

Short Answer

Expert verified
a. Probability for four is approximately 0.185. b. Probability for three or more is approximately 0.616.

Step by step solution

01

Define the Variables

In this problem, we are dealing with a binomial distribution. The probability of success (completing four years of college) is denoted as \( p = 0.28 \). The number of individuals, or trials, \( n \), is 15.
02

Use the Binomial Probability Formula

To find the probability that exactly four individuals completed four years of college, use the binomial probability formula: \[ P(X = k) = \binom{n}{k} p^k (1-p)^{n-k} \] where \( n = 15 \), \( k = 4 \), and \( p = 0.28 \).
03

Calculate \( \binom{n}{k} \)

Calculate the binomial coefficient: \[ \binom{15}{4} = \frac{15!}{4!(15-4)!} = 1365 \]
04

Compute the Probability of Exactly Four Completing College

Substitute the values into the binomial formula: \[ P(X = 4) = 1365 \times (0.28)^4 \times (0.72)^{11} \] Calculate the probability.
05

Calculate Probability for Three or More

To find the probability of three or more completing college, calculate for each relevant value of \( k \) from 3 to 15 and sum the results: \[ P(X \geq 3) = P(X = 3) + P(X = 4) + \ldots + P(X = 15) \] You'll need to use the binomial formula repeatedly or a binomial calculator/table to facilitate this step.
06

Sum Probabilities (Cumulative Binomial Probability)

Calculate each probability: \[ P(X = 3), P(X = 4), \ldots, P(X = 15) \] and sum them together to get \( P(X \geq 3) \).

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Key Concepts

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

Probability Theory
Understanding probability theory is key to solving problems involving uncertain outcomes. Simply put, probability is the measure of the likelihood that a particular event will occur. It ranges from 0 to 1, where 0 means the event never happens, and 1 means it always does. Probability theory helps us quantify this likelihood in various experiments and real-world scenarios.
  • In the context of our exercise, we're interested in finding out how likely it is that a certain number of individuals, from a sample, have completed four years of college.
  • This problem uses the binomial distribution, which is a specific type of probability distribution applicable when dealing with binary outcomes (e.g., success or failure, yes or no).
The binomial distribution is defined by two parameters: the number of trials, denoted as \(n\), and the probability of success in each trial, \(p\). Here, "trials" represents the 15 sampled individuals, and "success" means they've completed college. The solution utilizes the binomial probability formula to determine these probabilities, an essential tool in probability theory.
Census Data
Census data provides a critical source of detailed demographic information that statisticians and researchers use to analyze population trends. Such data includes various statistics, like the percentage of individuals completing college, which can give us insights into education levels across a population.
  • In our exercise, the statistic from the Census Bureau's survey shows 28% have completed four years of college.
  • This data point becomes crucial for setting the probability \(p = 0.28\) in our binomial distribution problem.
Census data serves as a foundation for many analyses and can influence decisions in public policy, education planning, and societal assessments. By understanding the demographic spread, governments and institutions can allocate resources more efficiently. In statistical exercises, these percentages (like the 28% college completion) are used as known values to compute probability scenarios related to the population they represent.
Statistical Analysis
Statistical analysis involves collecting, reviewing, and interpreting data to uncover patterns and trends. It allows us to make informed predictions and decisions based on data rather than mere supposition. While solving our problem, statistical analysis is applied by processing data through the binomial distribution framework to draw meaningful conclusions.
  • First, defined parameters (such as \(n = 15\) and \(p = 0.28\)) set the stage for a rigorous calculation of probabilities.
  • Using the formula \( P(X = k) = \binom{n}{k} p^k (1-p)^{n-k} \), we find the likelihood of exact outcomes (e.g., exactly four people having completed college).
To explore multiple outcomes at once, cumulative probabilities are calculated, providing answers to broader questions (like the probability of "at least" a certain number achieving an outcome). These techniques are central to statistical analysis, allowing for the translation of raw data into actionable insights, informing decisions in diverse fields such as education, healthcare, and business.

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Most popular questions from this chapter

In San Francisco, \(30 \%\) of workers take public transportation daily (USA Today, December 21,2005). a. In a sample of 10 workers, what is the probability that exactly three workers take public transportation daily? b. In a sample of 10 workers, what is the probability that at least three workers take public transportation daily?

Nine percent of undergraduate students carry credit card balances greater than \(\$ 7000\) (Reader's Digest, July 2002 ). Suppose 10 undergraduate students are selected randomly to be interviewed about credit card usage. a. Is the selection of 10 students a binomial experiment? Explain. b. What is the probability that two of the students will have a credit card balance greater than \(\$ 7000 ?\) c. What is the probability that none will have a credit card balance greater than \(\$ 7000 ?\) d. What is the probability that at least three will have a credit card balance greater than \(\$ 7000 ?\)

A poll conducted by Zogby International showed that of those Americans who said music plays a "very important" role in their lives, \(30 \%\) said their local radio stations "always" play the kind of music they like (http://www.zogby.com, January 12,2004 ). Suppose a sample of 800 people who say music plays an important role in their lives is taken. a. How many would you expect to say that their local radio stations always play the kind of music they like? b. What is the standard deviation of the number of respondents who think their local radio stations always play the kind of music they like? c. What is the standard deviation of the number of respondents who do not think their local radio stations always play the kind of music they like?

Through the week ending September 16,2001 , Tiger Woods was the leading money winner on the PGA Tour, with total earnings of \(\$ 5,517,777 .\) Of the top 10 money winners, seven players used a Titleist brand golf ball (http://www.pgatour.com). Suppose that we randomly select two of the top 10 money winners. a. What is the probability that exactly one uses a Titleist golf ball? b. What is the probability that both use Titleist golf balls? c. What is the probability that neither uses a Titleist golf ball?

When a new machine is functioning properly, only \(3 \%\) of the items produced are defective. Assume that we will randomly select two parts produced on the machine and that we are interested in the number of defective parts found. a. Describe the conditions under which this situation would be a binomial experiment. b. Draw a tree diagram similar to Figure 5.3 showing this problem as a two- trial experiment. c. How many experimental outcomes result in exactly one defect being found? d. Compute the probabilities associated with finding no defects, exactly one defect, and two defects.

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