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The article "Examined Life: What Stanley H. Kaplan Taught Us About the SAT" (The New Yorker [December 17,2001\(]: 86-92\) ) included a summary of findings regarding the use of SAT I scores, SAT II scores, and high school grade point average (GPA) to predict first-year college GPA. The article states that "among these, SAT II scores are the best predictor, explaining 16 percent of the variance in first-year college grades. GPA was second at \(15.4\) percent, and SAT I was last at \(13.3\) percent." a. If the data from this study were used to fit a leastsquares line with \(y=\) first-year college \(\mathrm{GPA}\) and \(x=\) high school GPA, what would the value of \(r^{2}\) have been? b. The article stated that SAT II was the best predictor of first-year college grades. Do you think that predictions based on a least-squares line with \(y=\) first-year college GPA and \(x=\) SAT II score would have been very accurate? Explain why or why not.

Short Answer

Expert verified
a) The value of \(r^{2}\) would have been 0.154. b) The predictions based on SAT II scores could be a relatively good predictor, but they would not be very accurate overall since the SAT II only explains 16 percent of the variance in college grades.

Step by step solution

01

Identify and Understand Given Values

From the exercise posed, we are told that GPA explains 15.4 percent of the variance in first-year college grades.
02

Definition of Coefficient of Determination

It's vital to remember that the coefficient of determination, denoted by \(r^{2}\), is the proportion of the variance in the dependent variable (first-year college GPA in this case) that is predictable from the independent variable(s) (high school GPA). It is also expressed as a percentage, which makes it directly comparable to the percentage of variance explained.
03

Calculate the Coefficient of Determination

Since the high school GPA explains 15.4 percent of the variance in first-year college grades, the coefficient of determination, \(r^{2}\), will also be 0.154. This is because the coefficient of determination is equivalent to the percentage of variance explained.
04

Evaluate the Potential Accuracy of the Prediction

SAT II score explains 16 percent of the variance, which is higher than the GPA explaining 15.4 percent. However, even though SAT II score is the 'best' predictor among the three, it still only explains 16 percent of the variance. Therefore, while SAT II might be a good metric for prediction, 84% of the variance is caused by other factors not included in our model, which means the prediction will not be very accurate.

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Key Concepts

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

Understanding SAT II Scores
SAT II scores, also known as SAT Subject Test scores, are designed to measure a student's knowledge in specific high school subjects. The use of these scores in the context of the given exercise revolves around how well they predict a student's future academic performance, particularly their first-year college GPA.

In evaluating the efficaciousness of SAT II scores as predictive tools, research suggests that they can be a good indicator of college success. They are designed to assess a student's proficiency in areas that often translate well to college-level work, such as mathematics, sciences, and languages.

However, it's crucial to note that while SAT II scores are valuable, they are not the sole determinant of college success. Predictive models based on SAT II scores can give insights into a student's readiness for college studies, but other factors such as high school GPA, extracurriculars, and personal circumstances also play significant roles.
Predicting College GPA
Predicting college GPA is a complex task that involves analyzing various academic metrics from a student's high school performance. Among the most commonly evaluated are SAT I and SAT II scores, as well as high school GPA. Each of these quantitative measures provides a distinct viewpoint.

The first-year college GPA is often seen as an important indicator of a student's potential for continued academic success. In the context of the original exercise, SAT II scores have been identified as the strongest predictor among the three variables mentioned. Nevertheless, with SAT II scores explaining only 16% of the variation in first-year college GPA, predicting college GPA remains imperfect.

It's important for students and educators to understand the limitations of prediction models. These models should be integrated with comprehensive assessments that account for less quantifiable predictors such as motivation, learning styles, and support systems.
Least Squares Regression and Coefficient of Determination
Least squares regression is a statistical method used to approximate the relationship between a dependent variable and one or more independent variables. The method minimizes the sum of the squares of the differences between observed values and the values predicted by the linear model.

The coefficient of determination, denoted as \(r^{2}\), captures how much of the dependent variable's variability can be explained by the model. A higher \(r^{2}\) value implies a better fit of the model to the data, meaning more of the variations can be explained by the independent variable(s).

In our original exercise, the \(r^{2}\) value for high school GPA as a predictor of college GPA would have been 0.154, indicating that approximately 15.4% of the variance in college GPA could be explained by students' high school GPA. This data informs us that while there is some relationship worth considering, much of the outcome (in this case, college GPA) remains unaccounted for by the model, emphasizing the need to consider other factors beyond test scores and GPAs for a comprehensive prediction of college success.

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Most popular questions from this chapter

A sample of 548 ethnically diverse students from Massachusetts were followed over a 19 -month period from 1995 and 1997 in a study of the relationship between TV viewing and eating habits (Pediatrics [2003]: \(1321-\) 1326). For each additional hour of television viewed per day, the number of fruit and vegetable servings per day was found to decrease on average by \(0.14\) serving. a. For this study, what is the dependent variable? What is the predictor variable? b. Would the least-squares line for predicting number of servings of fruits and vegetables using number of hours spent watching TV as a predictor have a positive or negative slope? Explain.

Each individual in a sample was asked to indicate on a quantitative scale how willing he or she was to spend money on the environment and also how strongly he or she believed in God ("Religion and Attitudes Toward the Environment," Journal for the Scientific Study of Religion [1993]: \(19-28\) ). The resulting value of the sample correlation coefficient was \(r=-.085\). Would you agree with the stated conclusion that stronger support for environmental spending is associated with a weaker degree of belief in God? Explain your reasoning.

The paper "Increased Vital and Total Lung Capacities in Tibetan Compared to Han Residents of Lhasa" (American Journal of Physical Anthropology [1991]:341-351) included a scatterplot of vital capacity (y) versus chest circumference \((x)\) for a sample of 16 Tibetan natives, from which the following data were read: $$ \begin{array}{rrrrrrrrr} x & 79.4 & 81.8 & 81.8 & 82.3 & 83.7 & 84.3 & 84.3 & 85.2 \\ y & 4.3 & 4.6 & 4.8 & 4.7 & 5.0 & 4.9 & 4.4 & 5.0 \\ x & 87.0 & 87.3 & 87.7 & 88.1 & 88.1 & 88.6 & 89.0 & 89.5 \\ y & 6.1 & 4.7 & 5.7 & 5.7 & 5.2 & 5.5 & 5.0 & 5.3 \end{array} $$ a. Construct a scatterplot. What does it suggest about the nature of the relationship between \(x\) and \(y\) ? b. The summary quantities are $$ \sum x=1368.1 \quad \sum y=80.9 $$ \(\sum x y=6933.48 \quad \sum x^{2}=117,123.85 \quad \sum y^{2}=412.81\) Verify that the equation of the least-squares line is \(\hat{y}=\) \(-4.54+0.1123 x\), and draw this line on your scatterplot. c. On average, roughly what change in vital capacity is associated with a 1 -cm increase in chest circumference? with a 10 -cm increase? d. What vital capacity would you predict for a Tibetan native whose chest circumference is \(85 \mathrm{~cm} ?\) e. Is vital capacity completely determined by chest circumference? Explain.

Draw two scatterplots, one for which \(r=1\) and a second for which \(r=-1\).

An accurate assessment of oxygen consumption provides important information for determining energy expenditure requirements for physically demanding tasks. The paper "Oxygen Consumption During Fire Suppression: Error of Heart Rate Estimation" (Ergonomics [1991]: \(1469-1474\) ) reported on a study in which \(x=\) oxygen consumption (in milliliters per kilogram per minute) during a treadmill test was determined for a sample of 10 firefighters. Then \(y=\) oxygen consumption at a comparable heart rate was measured for each of the 10 individuals while they performed a fire-suppression simulation. This resulted in the following data and scatterplot: $$ \begin{array}{lrrrrr} \text { Firefighter } & 1 & 2 & 3 & 4 & 5 \\ x & 51.3 & 34.1 & 41.1 & 36.3 & 36.5 \\ y & 49.3 & 29.5 & 30.6 & 28.2 & 28.0 \\ \text { Firefighter } & 6 & 7 & 8 & 9 & 10 \\ x & 35.4 & 35.4 & 38.6 & 40.6 & 39.5 \\ y & 26.3 & 33.9 & 29.4 & 23.5 & 31.6 \end{array} $$ a. Does the scatterplot suggest an approximate linear relationship? b. The investigators fit a least-squares line. The resulting MINITAB output is given in the following:. Predict fire-simulation consumption when treadmill consumption is 40 . c. How effectively does a straight line summarize the relationship? d. Delete the first observation, \((51.3,49.3)\), and calculate the new equation of the least-squares line and the value of \(r^{2}\). What do you conclude? (Hint: For the original data, \(\sum x=388.8, \Sigma y=310.3, \sum x^{2}=15,338.54, \sum x y=\) \(12,306.58\), and \(\sum y^{2}=10,072.41\).)

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