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Use the following information to answer the next five exercises: Suppose that a group of statistics students is divided into two groups: business majors and non-business majors. There are 16 business majors in the group and seven non- business majors in the group. A random sample of nine students is taken. We are interested in the number of business majors in the sample. Find the standard deviation.

Short Answer

Expert verified
The standard deviation of the number of business majors in the sample is approximately 1.100.

Step by step solution

01

Define the Random Variables

Our random variable, \( X \), represents the number of business majors selected in the sample of nine students. We need to model this situation using a probability distribution.
02

Identify the Distribution Type

Since we are sampling without replacement from a finite population, the hypergeometric distribution is appropriate. The parameters are population size \( N = 23 \) (16 business majors + 7 non-business majors), number of success states in the population \( K = 16 \), and sample size \( n = 9 \).
03

Write the Formula for the Standard Deviation

The standard deviation of a hypergeometric distribution is given by \[ \sigma = \sqrt{n \cdot \left( \frac{K}{N} \right) \cdot \left( \frac{N-K}{N} \right) \cdot \frac{N-n}{N-1} } \] where \( n \) is the sample size, \( K \) is the number of success states, \( N \) is the population size.
04

Substitute the Values into the Formula

Substitute \( n = 9 \), \( K = 16 \), and \( N = 23 \) into the formula: \[ \sigma = \sqrt{9 \cdot \left( \frac{16}{23} \right) \cdot \left( \frac{7}{23} \right) \cdot \frac{14}{22} } \]
05

Calculate the Values

Calculate each component: \( \frac{16}{23} = 0.6957 \), \( \frac{7}{23} = 0.3043 \), \( \frac{14}{22} = 0.6364 \). Then, \( 9 \cdot 0.6957 \cdot 0.3043 \cdot 0.6364 = 1.2101 \). Take the square root to find \( \sigma \).
06

Find the Final Answer

Calculating the square root of 1.2101 gives the standard deviation: \( \sigma \approx 1.100 \).

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Key Concepts

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

Standard Deviation
In statistics, the standard deviation is a key metric that indicates how spread out numbers in a dataset are. When we discuss the standard deviation in the context of a hypergeometric distribution, we are specifically looking at how the counts of a particular success result from a finite population vary.

The general formula for standard deviation in the hypergeometric distribution is:
  • \( \sigma = \sqrt{n \cdot \left( \frac{K}{N} \right) \cdot \left( \frac{N-K}{N} \right) \cdot \frac{N-n}{N-1} } \)
Here:
  • \( n \) is the sample size,
  • \( K \) is the number of successes in the population,
  • \( N \) is the total population size.
The standard deviation helps us understand the variability of selecting a particular group, such as business majors in our problem. A smaller standard deviation indicates that the values are closer to the mean, while a large one suggests more variability.
Random Sampling
Random sampling is a fundamental concept in statistics where each member of a population has an equal chance of being selected. In this exercise, we create a sample from a larger population.

When students are picked for a study, such as determining how many are business majors, it's crucial to sample randomly to avoid biases. This holds especially when the order or identity of selected students could unduly influence the results of the study.

Random sampling allows us to make representative conclusions about our entire group without studying the whole population. By understanding random sampling, we ensure that our results reflect the broader group's characteristics, avoiding any undue biases present in systematic or non-random sampling methods.
Finite Population
A finite population refers to a set number of individuals or items within a population that can be counted fully. In this problem, the finite population consists of a total of 23 students, combining both business and non-business majors.

In situations involving a finite population, sampling without replacement is common. This essentially means that once a student is picked for the survey, they can't be chosen again, which is critical when using the hypergeometric distribution.

Understanding finite population concepts is essential because it helps differentiate between using statistical models like the hypergeometric distribution versus models used for infinite populations, like the binomial distribution.
Probability Distribution
Probability distributions are mathematical functions that provide the probabilities of occurrence of different possible outcomes in an experiment. For this exercise, we use the hypergeometric probability distribution.

The hypergeometric distribution is ideal for situations where objects are sampled without replacement from a finite population. It calculates the probability of drawing a specified number of successes (i.e., business majors in our example) in a fixed sample size.

Parameters of this distribution include:
  • Total population size \( N \)
  • Number of success states \( K \)
  • Sample size \( n \)
By understanding the probability distribution, you can better estimate how likely certain outcomes are, key in domains such as the quality control of products or determining election results.

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Most popular questions from this chapter

It has been estimated that only about 30% of California residents have adequate earthquake supplies. Suppose we are interested in the number of California residents we must survey until we find a resident who does not have adequate earthquake supplies. a. In words, define the random variable \(X.\) b. List the values that \(X\) may take on. c. Give the distribution of \(X . X \sim\) ____ (__,___) d. What is the probability that we must survey just one or two residents until we find a California resident who does not have adequate earthquake supplies? e. What is the probability that we must survey at least three California residents until we find a California resident who does not have adequate earthquake supplies? f. How many California residents do you expect to need to survey until you find a California resident who does not have adequate earthquake supplies? g. How many California residents do you expect to need to survey until you find a California resident who does have adequate earthquake supplies?

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Use the following information to answer the next two exercises: The probability that the San Jose Sharks will win any given game is 0.3694 based on a 13-year win history of 382 wins out of 1,034 games played (as of a certain date). An upcoming monthly schedule contains 12 games. The chance of an IRS audit for a tax return with over \(\$ 25,000\) in income is about 2% per year. We are interested in the expected number of audits a person with that income has in a 20-year period. Assume each year is independent. a. In words, define the random variable \( X\). b. List the values that \(X\) may take on. c. Give the distribution of \(X . X \sim\) ___ (___,____) d. How many audits are expected in a 20-year period? e. Find the probability that a person is not audited at all. f. Find the probability that a person is audited more than twice.

Use the following information to answer the next four exercises: Ellen has music practice three days a week. She practices for all of the three days 85% of the time, two days 8% of the time, one day 4% of the time, and no days 3% of the time. One week is selected at random. Construct a probability distribution table for the data.

Use the following information to answer the next six exercises: On average, eight teens in the U.S. die from motor vehicle injuries per day. As a result, states across the country are debating raising the driving age. Is it likely that there will be more than 20 teens killed from motor vehicle injuries on any given day in the U.S.? Justify your answer numerically.

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