/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 66 Exercises 65 and 66 refer to the... [FREE SOLUTION] | 91Ó°ÊÓ

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Exercises 65 and 66 refer to the following setting. Scores on the mathematics part of the SAT exam in a recent year were roughly Normal with mean 515 and standard deviation \(114 .\) You choose an SRS of 100 students and average their SAT Math scores. Suppose that you do this many, many times. The standard deviation of the average scores you get should be close to (a) \(114 .\) (b) \(114 / 100=1.14\) (c) \(114 / \sqrt{100}=11.4\) (d) 1 (e) none of these.

Short Answer

Expert verified
11.4; correct option is (c).

Step by step solution

01

Understand the Concept of Sampling Distribution

When discussing the average scores of many samples, we refer to the sampling distribution of the sample mean. The concept is that the averages of samples of size 100 will themselves form a normal distribution around the population mean.
02

Determine the Formula for the Standard Deviation of the Sample Mean

For a sampling distribution of the sample mean, the standard deviation (also known as standard error) is calculated using the formula: \( \sigma_{\bar{x}} = \frac{\sigma}{\sqrt{n}} \), where \( \sigma \) is the population standard deviation and \( n \) is the sample size.
03

Calculate the Standard Deviation of the Sample Mean

Given \( \sigma = 114 \) and \( n = 100 \), substitute them into the formula: \( \sigma_{\bar{x}} = \frac{114}{\sqrt{100}} = \frac{114}{10} = 11.4 \).
04

Match the Calculation with the Provided Options

The calculated standard deviation of the sample mean is 11.4. Comparing this with the options provided: (a) 114, (b) 1.14, (c) 11.4, (d) 1, (e) none of these, the correct answer is (c) 11.4.

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Key Concepts

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

Sampling Distribution
When dealing with large sets of data, especially in statistics, we often come across the term "sampling distribution." Simply put, a sampling distribution is the distribution of a statistic (like the mean) calculated from multiple samples of the same size drawn from the same population. This is fundamental when trying to make inferences about a population based on a limited set of data.

For instance, in the exercise, we look at the average SAT Math scores from numerous samples of 100 students each. Each sample mean forms part of what we call the sampling distribution of the sample mean. This new distribution will have its own mean, typically very close to the original population mean, and its own standard deviation.
  • The process helps statisticians understand how the sample mean relates to the true population.
  • Based on the Law of Large Numbers, as the number of samples increases, the sample mean gets closer to the population mean.
By averaging over many samples, we can better estimate the characteristic properties of the population.
Standard Deviation
The standard deviation is a critical concept in statistics. It measures how spread out the values in a data set are and is crucial for understanding data variability. For a given data set, a high standard deviation means data points are spread out over a wide range, while a low one indicates they cluster around the mean.

In the context of the SAT Math scores, the population standard deviation is given as 114. This informs us about the variability of students' scores around the mean score of 515.
  • This variability helps predict how often scores fall within certain ranges.
  • For sample data, understanding the spread helps ensure better statistical accuracy and reliability.
When dealing with sample means, we also talk about the "standard error," which is the standard deviation of the sampling distribution of sample means.
SAT Mathematics Score
The SAT Mathematics Score is a component of the SAT exam, which assesses a student's readiness for college. The importance of understanding SAT scores lies in their widespread use in college admissions, making them a critical benchmark for high school students in the United States.

The scores in the SAT Math section are normally distributed, with a specified mean and standard deviation. This particular exercise highlights a mean score of 515 and a standard deviation of 114, indicating how most students perform around this average.
  • This type of distribution helps schools and universities understand a student's relative standing among peers.
  • Knowing this distribution allows for fair statistical comparisons.
By analyzing these distributions, institutions can make data-driven decisions when considering students during the admissions process.
Normal Distribution
The normal distribution is a continuous probability distribution that is symmetrical around its mean, depicting the distribution of a dataset. It's often described as a bell curve due to its shape and is foundational in statistics because many real-world variables, such as SAT Math scores, follow this pattern.

Key features of the normal distribution include:
  • Mean, median, and mode are all equal and located at the center of the distribution.
  • The curve is symmetric about the mean.
  • Approximately 68% of data falls within one standard deviation of the mean, 95% within two, and 99.7% within three, known as the 68-95-99.7 rule.
Understanding this distribution allows statisticians to infer probabilities and make predictions about data sets. In this case, it helps understand how SAT Math scores are distributed around the average, providing insights into how likely a student’s score is to fall within a specific range.

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Most popular questions from this chapter

Run a mile During World War II, \(12,000\) able bodied male undergraduates at the University of Illinois participated in required physical training. Each student ran a timed mile. Their times followed the Normal distribution with mean 7.11 minutes and standard deviation 0.74 minute. An SRS of 100 of these students has mean time \(\overline{x}=7.15\) minutes. A second SRS of size 100 has mean \(\overline{x}=6.97\) minutes. After many SRSs, the values of the sample mean \(\overline{x}\) follow the Normal distribution with mean \(7.11 \mathrm{minutes}-\) and standard deviation 0.074 minute. (a) What is the population? Describe the population distribution. (b) Describe the sampling distribution of \(\overline{x} .\) How is it different from the population distribution?

Multiple choice: Select the best answer for Exercises 43 to \(46,\) which refer to the following setting. The magazine Sports Illustrated asked a random sample of 750 Division I college athletes, "Do you believe performance- enhancing drugs are a problem in college sports?" Suppose that 30\(\%\) of all Division I athletes think that these drugs are a problem. Let \(\hat{p}\) be the sample proportion who say that these drugs are a problem. The sampling distribution of \(\hat{p}\) is approximately Normal because (a) there are at least 7570 Division I college athletes. (b) \(n p=225\) and \(n(1-p)=525\) (c) a random sample was chosen. (d) a large sample size like \(n=750\) guarantees it. (e) the sampling distribution of \(\hat{\rho}\) always has this shape.

Sharing music online \((5.2)\) A sample survey reports that 29\(\%\) of Internet users download music fles online, 21\(\%\) share music fles from their computers, and 12\(\%\) both download and share music. 6 Make a Venn diagram that displays this information. What percent of Internet users neither download nor share music files?

On-time shipping Your mail-order company advertises that it ships 90\(\%\) of its orders within three working days. You select an SRS of 100 of the 5000 orders received in the past week for an audit. The audit reveals that 86 of these orders were shipped on time. (a) If the company really ships 90\(\%\) of its orders on time, what is the probability that the proportion in an SRS of 100 orders is as small as the proportion in your sample or smaller? Follow the four-step process. (b) A critic says, "Aha! You claim \(90 \%,\) but in your sample the on-time percentage is lower than that. So the 90\(\%\) claim is wrong." Explain in simple language why your probability calculation in shows that the result of the sample does not refute the 90\(\%\) claim.

For Exercises 1 to \(4,\) identify the population, the parameter, the sample, and the statistic in each setting. Unemployment Each month, the Current Population Survey interviews a random sample of individuals in about \(55,000\) U.S. households. One of their goals is to estimate the national unemployment rate. In December \(2009,10.0 \%\) of those interviewed were unemployed.

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