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Eleanor scores 680 on the SAT Mathematics test. The distribution of SAT scores is symmetric and single-peaked, with mean 500 and standard deviation 100 . Gerald takes the American College Testing (ACT) Mathematics test and scores 27. ACT scores also follow a symmetric, single-peaked distribution-but with mean 18 and standard deviation \(6 .\) Find the standardized scores for both students. Assuming that both tests measure the same kind of ability, who has the higher score?

Short Answer

Expert verified
Eleanor has the higher score with a Z-score of 1.8 compared to Gerald's 1.5.

Step by step solution

01

Understand the Z-Score Formula

The Z-score formula is used to find how many standard deviations an element is from the mean. The formula for the Z-score is given by: \( Z = \frac{X - \mu}{\sigma} \), where \( X \) is the value of the element, \( \mu \) is the mean of the distribution, and \( \sigma \) is the standard deviation of the distribution.
02

Calculate Eleanor's Z-Score

Eleanor's SAT Mathematics score is 680. The mean \( \mu \) for SAT is 500 and the standard deviation \( \sigma \) is 100. Using the formula: \[ Z_{\text{SAT}} = \frac{680 - 500}{100} \] \[ Z_{\text{SAT}} = \frac{180}{100} = 1.8 \] Eleanor's Z-score is 1.8.
03

Calculate Gerald's Z-Score

Gerald's ACT Mathematics score is 27. The mean \( \mu \) for ACT is 18 and the standard deviation \( \sigma \) is 6. Using the formula: \[ Z_{\text{ACT}} = \frac{27 - 18}{6} \] \[ Z_{\text{ACT}} = \frac{9}{6} = 1.5 \] Gerald's Z-score is 1.5.
04

Compare the Z-Scores

Eleanor has a Z-score of 1.8, while Gerald has a Z-score of 1.5. Since a higher Z-score indicates a score that is further from the mean in the positive direction, Eleanor has the higher score relative to others who took the same test.

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Key Concepts

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

sat mathematics
The SAT Mathematics section is part of a standardized test used in the United States for college admissions. It is designed to assess mathematical reasoning and problem-solving skills of high school students. The SAT Mathematics section consists of questions that cover a range of topics, such as algebra, problem-solving with data, and some aspects of geometry. Scores from the SAT Mathematics section can fall between 200 and 800.

For SAT Mathematics, the distribution of scores is usually symmetrical and single-peaked. This means that most students' scores cluster around the mean, creating a bell-shaped curve. For example, if the mean SAT Mathematics score is 500 with a standard deviation of 100, like in Eleanor's case, we can expect most scores to fall within a few hundred points of the mean. Understanding the distribution is crucial when comparing scores to assess how they relate to the overall performance of all test-takers.
act mathematics
The ACT Mathematics section is part of another standardized test used for college admissions in the United States. It similarly evaluates students' mathematical skills and their ability to solve problems effectively. The types of questions on the ACT Mathematics test include algebra, coordinate geometry, and trigonometry.

Scores for the ACT Mathematics section range from 1 to 36, and unlike the SAT, the ACT typically provides a different mean and standard deviation. In Gerald's case, an ACT Mathematics mean score of 18 with a standard deviation of 6 indicates how students generally perform on this test. Understanding these metrics is helpful for estimating how well a student, like Gerald, performed in comparison to other test-takers.
z-score
The concept of a Z-score is fundamental in statistics, especially for comparing scores from different distributions. A Z-score determines how far away a given score is from the mean in terms of standard deviations. This is invaluable when making comparisons, as it standardizes scores across different tests.

To calculate the Z-score, use the formula: \[ Z = \frac{X - \mu}{\sigma} \] where:
  • \(X\) = the individual score
  • \(\mu\) = the mean of the distribution
  • \(\sigma\) = the standard deviation of the distribution
Using this formula, Eleanor's SAT Mathematics score yields a Z-score of 1.8, and Gerald's ACT Mathematics score results in a Z-score of 1.5. This means Eleanor's score is 1.8 standard deviations above the SAT mean, and Gerald's is 1.5 standard deviations above the ACT mean.
mean and standard deviation
Two critical metrics in statistics are the mean and standard deviation. The mean is the average of all scores, providing a central point in the dataset. The standard deviation measures how spread out the numbers in the distribution are. It offers insight into the amount of variation or dispersion present.

In our exercise, SAT scores have a mean of 500 and a standard deviation of 100. This tells us that most test-takers score within this range, with deviations indicating how scores vary. Similarly, ACT scores with a mean of 18 and a standard deviation of 6 illustrate that scores are normally distributed but with a smaller spread compared to SAT, given standardized testing differences.

Grasping these concepts allows students to understand not only the central tendency but also how much variability exists in scores, leading to better interpretations of individual performance relative to peers.
score comparison
Comparing scores from different tests requires understanding concepts like the Z-score, mean, and standard deviation. Because SAT and ACT mathematics scores are usually distributed differently, directly comparing the raw scores is not effective.

However, by using Z-scores, we can determine which student performed better when comparing relative performance across different tests. For instance, Eleanor's Z-score of 1.8 indicates her SAT Mathematics score is further from the mean than Gerald's ACT Mathematics Z-score of 1.5. Thus, it can be concluded that Eleanor performed better relative to her peers than Gerald did. Such comparisons are valuable in contexts like college admissions where understanding the relative prowess of students is necessary.

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Most popular questions from this chapter

Sharks Here are the lengths in feet of 44 great white sharks: \({ }^{11}\) $$ \begin{array}{llllllllll} \hline 18.7 & 12.3 & 18.6 & 16.4 & 15.7 & 18.3 & 14.6 & 15.8 & 14.9 & 17.6 & 12.1 \\ 16.4 & 16.7 & 17.8 & 16.2 & 12.6 & 17.8 & 13.8 & 12.2 & 15.2 & 14.7 & 12.4 \\ 13.2 & 15.8 & 14.3 & 16.6 & 9.4 & 18.2 & 13.2 & 13.6 & 15.3 & 16.1 & 13.5 \\ 19.1 & 16.2 & 22.8 & 16.8 & 13.6 & 13.2 & 15.7 & 19.7 & 18.7 & 13.2 & 16.8 \\ \hline \end{array} $$ (a) Enter these data into your calculator and make a histogram. Include a sketch of the graph on your paper. Then calculate one-variable statistics. Describe the shape, center, and spread of the distribution of shark lengths. (b) Calculate the percent of observations that fall within 1 , 2, and 3 standard deviations of the mean. How do these results compare with the \(68-95-99.7\) rule? (c) Use your calculator to construct a Normal probability plot. Include a sketch of the graph on your paper. Interpret this plot. (d) Having inspected the data from several different perspectives, do you think these data are approximately Normal? Write a brief summary of your assessment that combines your findings from parts (a) through (c).

Density curves Sketch a density curve that might describe a distribution that has a single peak and is skewed to the left.

George has an average bowling score of 180 and bowls in a league where the average for all bowlers is 150 and the standard deviation is \(20 .\) Bill has an average bowling score of 190 and bowls in a league where the average is 160 and the standard deviation is \(15 .\) Who ranks higher in his own league, George or Bill? (a) Bill, because his 190 is higher than George's 180 . (b) Bill, because his standardized score is higher than George's. (c) Bill and George have the same rank in their leagues, because both are 30 pins above the mean. (d) George, because his standardized score is higher than Bill's. (e) George, because the standard deviation of bowling scores is higher in his league.

Weights aren't Normal The heights of people of the same gender and similar ages follow Normal distributions reasonably closely. Weights, on the other hand, are not Normally distributed. The weights of women aged 20 to 29 have mean 141.7 pounds and median 133.2 pounds. The first and third quartiles are 118.3 pounds and 157.3 pounds. What can you say about the shape of the weight distribution? Why?

Density of the earth In 1798 , the English scientist Henry Cavendish measured the density of the earth several times by careful work with a torsion balance. The variable recorded was the density of the earth as a multiple of the density of water. Here are Cavendish's 29 measurements: \({ }^{12}\) $$ \begin{array}{llllllllll} \hline 5.50 & 5.61 & 4.88 & 5.07 & 5.26 & 5.55 & 5.36 & 5.29 & 5.58 & 5.65 \\ 5.57 & 5.53 & 5.62 & 5.29 & 5.44 & 5.34 & 5.79 & 5.10 & 5.27 & 5.39 \\ 5.42 & 5.47 & 5.63 & 5.34 & 5.46 & 5.30 & 5.75 & 5.68 & 5.85 & \\ \hline \end{array} $$ (a) Enter these data into your calculator and make a histogram. Include a sketch of the graph on your paper. Then calculate one-variable statistics. Describe the shape, center, and spread of the distribution of density measurements. (b) Calculate the percent of observations that fall within \(1,2,\) and 3 standard deviations of the mean. How do these results compare with the \(68-95-99.7\) rule? (c) Use your calculator to construct a Normal probability plot. Include a sketch of the graph on your paper. Interpret this plot. (d) Having inspected the data from several different perspectives, do you think these data are approximately Normal? Write a brief summary of your assessment that combines your findings from parts (a) through (c).

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