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Ch. 9 - Correlation and Regression
Larson - Elementary Statistics: Picturing the World 8th Edition
Larson8th EditionElementary Statistics: Picturing the WorldISBN: 9780137493470Not the one you use?Change textbook
Chapter 9, Problem 9.1.32

In Exercise 26, add data for an international soccer player who can perform the half squat with a maximum of 210 kilograms and can sprint 10 meters in 2.00 seconds. Describe how this affects the correlation coefficient r.

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1
Understand the problem: The task involves adding a new data point to an existing dataset and analyzing how this new data point affects the correlation coefficient (r). The correlation coefficient measures the strength and direction of the linear relationship between two variables—in this case, maximum squat weight and sprint time.
Identify the variables: The two variables are (1) maximum squat weight (in kilograms) and (2) sprint time (in seconds). The new data point is (210, 2.00).
Determine the impact of the new data point: Consider whether the new data point aligns with the existing trend in the dataset. If the new data point strengthens the linear relationship, the magnitude of r will increase (closer to 1 or -1). If it weakens the relationship, the magnitude of r will decrease (closer to 0).
Recalculate the correlation coefficient: Use the formula for the Pearson correlation coefficient: r=(x-x¯)(y-y¯)(x-x¯)2(y-y¯)2. Here, x represents squat weight, y represents sprint time, and x̄ and ȳ are their respective means. Add the new data point to the dataset and compute the updated r.
Interpret the result: After recalculating r, compare it to the original value. If the new data point is consistent with the existing trend, r will likely increase in magnitude. If it deviates significantly from the trend, r will decrease in magnitude. This interpretation helps understand the influence of the new data point on the relationship between squat weight and sprint time.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Correlation Coefficient (r)

The correlation coefficient, denoted as r, quantifies the strength and direction of a linear relationship between two variables. It ranges from -1 to 1, where 1 indicates a perfect positive correlation, -1 a perfect negative correlation, and 0 no correlation. Understanding r is crucial for interpreting how changes in one variable may relate to changes in another, such as the relationship between an athlete's strength and speed.
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Half Squat Performance

The half squat is a strength training exercise that targets the lower body, particularly the quadriceps, hamstrings, and glutes. An athlete's ability to perform a half squat with a maximum weight, such as 210 kilograms, can indicate their overall strength and power. This performance metric can be correlated with other athletic abilities, such as sprinting speed, to assess how strength influences speed in sports.
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Sprinting Speed

Sprinting speed refers to the time it takes an athlete to cover a specific distance, in this case, 10 meters in 2.00 seconds. This measure is critical in sports performance, as it reflects an athlete's explosive power and acceleration. Analyzing the relationship between sprinting speed and strength metrics, like half squat performance, can provide insights into how these physical attributes interact and contribute to overall athletic performance.
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Related Practice
Textbook Question

"Constructing and Interpreting a Prediction Interval In Exercises 21-30, construct the indicated prediction interval and interpret the results.

26. Voter Turnout Construct a 99% prediction interval for number of ballots cast in Exercise 16 when the voting age population is 210 million."

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Textbook Question

"9. Stock Price The equation used to predict the stock price (in dollars) at the end of the year for a restaurant chain is y=- 86+7.46x_1 - 1.61x_2

where x_1 is the total revenue (in billions of dollars) and x_2 is the shareholders' equity (in

billions of dollars). Use the multiple regression equation to predict the y-values for the

values of the independent variables.

a. x_1 = 27.6, x_2 = 15.3

b. x_1 = 24.1, x_2 = 14.6

c. x_1 = 23.5, x_2 = 13.4

d. x_1 = 22.8, x_2 =15.3"

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Textbook Question

"In Exercises 7-10, use the value of the correlation coefficient r to calculate the coefficient of determination r^2. What does this tell you about the explained variation of the data about the regression line? about the unexplained variation?

10. r =0.881"

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Textbook Question

"Confidence Intervals for y-Intercept and Slope

You can construct confidence intervals for the y-intercept B and slope M of the regression line y = Mx + B for the population by using the inequalities below.

y-intercept B :

b - E < B < b + E

where

E = t_c s_e \(\sqrt{\frac{1}{n}\) + \(\frac{\overline{x}\)^2}{\(\sum\) x^2 - \(\frac{(\Sigma x)^2}{n}\)}}

slope M :

m - E < M < m + E

where

E = \(\frac{t_c s_e}{\sqrt{\sum x^2 - \frac{(\Sigma x)^2}{n}\)}}

The values of m and b are obtained from the sample data, and the critical value t_c is found using Table 5 in Appendix B with n - 2 degrees of freedom.

In Exercises 37 and 38, construct the indicated confidence intervals for B and M using the gross domestic products and carbon dioxide emissions data found in Example 2.

38. 99% confidence interval"

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Textbook Question

"[APPLET] For Exercises 1–8, use the data in the table, which shows the average annual salaries (both in thousands of dollars) for secondary and elementary school teachers, excluding special and vocational education teachers, in the United States for 11 years. (Source: U.S. Bureau of Labor Statistics)

8. Construct a 95% prediction interval for the average annual salary of elementary school teachers when the average annual salary of secondary school teachers is \$63,500. Interpret the results."

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Textbook Question

"In Exercises 17 and 18, use the data to (a) find the coefficient of determination r^2 and interpret

the result, and (b) find the standard error of estimate s_e and interpret the result.


18. [APPLET] The table shows the cooking areas (in square inches) of 18 gas grills and their prices (in dollars). The regression equation is y = 1.501x - 341.501. (Source: Lowe's)

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