Table of contents
- 1. Intro to Stats and Collecting Data55m
- 2. Describing Data with Tables and Graphs1h 55m
- 3. Describing Data Numerically1h 45m
- 4. Probability2h 16m
- 5. Binomial Distribution & Discrete Random Variables2h 33m
- 6. Normal Distribution and Continuous Random Variables1h 38m
- 7. Sampling Distributions & Confidence Intervals: Mean1h 3m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 12m
- 9. Hypothesis Testing for One Sample1h 1m
- 10. Hypothesis Testing for Two Samples2h 8m
- 11. Correlation48m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 20m
- 14. ANOVA1h 0m
3. Describing Data Numerically
Standard Deviation
Problem 10.3.5
Textbook Question
Interpreting the Coefficient of Determination
In Exercises 5–8, use the value of the linear correlation coefficient r to find the coefficient of determination and the percentage of the total variation that can be explained by the linear relationship between the two variables.
Times of Taxi Rides and Tips r = 0.298 (x = time in minutes, y = the amount of tip in dollars)

1
Step 1: Recall the formula for the coefficient of determination (R²), which is the square of the linear correlation coefficient r. The formula is R² = r².
Step 2: Substitute the given value of r (0.298) into the formula. This means you will calculate R² = (0.298)².
Step 3: Interpret the coefficient of determination (R²). It represents the proportion of the total variation in the dependent variable (y, the amount of tip in dollars) that can be explained by the linear relationship with the independent variable (x, time in minutes).
Step 4: To express this as a percentage, multiply the value of R² by 100. This will give you the percentage of the total variation in tips that can be explained by the time of the taxi ride.
Step 5: Conclude that the remaining percentage (100% - R²%) represents the variation in tips that cannot be explained by the linear relationship with time and may be due to other factors or randomness.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Coefficient of Determination (R²)
The coefficient of determination, denoted as R², quantifies the proportion of variance in the dependent variable that can be explained by the independent variable in a regression model. It ranges from 0 to 1, where 0 indicates no explanatory power and 1 indicates perfect explanation. In this context, R² is calculated as the square of the correlation coefficient (r), providing insight into the strength of the linear relationship between the two variables.
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Correlation Coefficient
Linear Correlation Coefficient (r)
The linear correlation coefficient, represented as r, measures the strength and direction of a linear relationship between two variables. Its value ranges from -1 to 1, where values close to 1 indicate a strong positive correlation, values close to -1 indicate a strong negative correlation, and values around 0 suggest no linear correlation. In the given example, r = 0.298 indicates a weak positive correlation between taxi ride times and tips.
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Total Variation
Total variation refers to the overall variability present in a dataset, which can be partitioned into explained variation and unexplained variation. In the context of regression analysis, explained variation is the portion of total variation that is accounted for by the model, while unexplained variation is the portion that remains after fitting the model. Understanding total variation is crucial for interpreting R², as it provides a baseline for assessing how well the model captures the data's variability.
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