In Exercise 23, add data for a child who is 6 years old and has a vocabulary of 900 words. Describe how this affects the correlation coefficient r.
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11. Correlation
Correlation Coefficient
Problem 4.1.25
Textbook Question
The TIMMS Exam The Trends in International Mathematics and Science (TIMMS) is a mathematics and science achievement exam given internationally. On each exam, students are asked to respond to a variety of background questions. For the 41 nations that participated in TIMMS, the correlation between the percentage of items answered in the background questionnaire (used as a proxy for student task persistence) and mean score on the exam was 0.79. Does this suggest there is a linear relation between student task persistence and achievement score? Write a sentence that explains what this result might mean.
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Step 1: Understand what the correlation coefficient represents. The correlation coefficient, denoted as \(r\), measures the strength and direction of a linear relationship between two variables. It ranges from -1 to 1, where values close to 1 or -1 indicate a strong linear relationship, and values near 0 indicate little to no linear relationship.
Step 2: Identify the given correlation value. Here, the correlation between the percentage of items answered (student task persistence) and mean exam score is \(r = 0.79\).
Step 3: Interpret the magnitude and sign of the correlation. Since \$0.79$ is a positive value close to 1, it suggests a strong positive linear relationship between task persistence and achievement score. This means that as task persistence increases, the achievement score tends to increase as well.
Step 4: Consider the context and limitations. While a correlation of 0.79 indicates a strong association, it does not imply causation. Other factors might influence the relationship, and further analysis would be needed to establish cause and effect.
Step 5: Formulate a clear explanatory sentence. For example, you might say: "The correlation of 0.79 suggests that there is a strong positive linear relationship between student task persistence and achievement score on the TIMMS exam, indicating that students who persist more tend to have higher scores."
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Correlation Coefficient
The correlation coefficient measures the strength and direction of a linear relationship between two variables, ranging from -1 to 1. A value of 0.79 indicates a strong positive linear association, meaning as one variable increases, the other tends to increase as well.
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Linear Relationship
A linear relationship implies that changes in one variable are associated with proportional changes in another, forming a straight-line pattern when graphed. A high correlation suggests such a relationship, but it does not prove causation or rule out other types of relationships.
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Interpretation of Statistical Results
Interpreting statistical results involves understanding what the numbers imply about real-world phenomena. Here, a correlation of 0.79 suggests a strong link between task persistence and achievement scores, but it should be explained carefully, noting that correlation does not imply causation.
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