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Ch. 10 - Correlation and Regression
Triola - Elementary Statistics 14th Edition
Triola14th EditionElementary StatisticsISBN: 9780137366446Not the one you use?Change textbook
Chapter 10, Problem 10.5.14

Finding the Best Model
In Exercises 5–16, construct a scatterplot and identify the mathematical model that best fits the given data. Assume that the model is to be used only for the scope of the given data, and consider only linear, quadratic, logarithmic, exponential, and power models.
Sunspot Numbers Listed below in order by row are annual sunspot numbers beginning with 1980. Is the best model a good model? Carefully examine the scatterplot and identify the pattern of the points. Which of the models fits that pattern?
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Step 1: Begin by plotting the given data points on a scatterplot. Use the x-axis to represent the years (e.g., 1980, 1981, etc.) and the y-axis to represent the corresponding sunspot numbers. This will help visualize the relationship between the two variables.
Step 2: Examine the scatterplot to identify the general pattern of the data points. Look for trends such as linearity, curvature, or exponential growth/decay. This will give you an idea of which type of model might fit the data best.
Step 3: Test different mathematical models (linear, quadratic, logarithmic, exponential, and power) by fitting each model to the data. This can be done using statistical software or a graphing calculator. For each model, calculate the corresponding regression equation.
Step 4: Evaluate the goodness of fit for each model. Use metrics such as the coefficient of determination (R²) to determine how well each model explains the variability in the data. The model with the highest R² value is typically the best fit.
Step 5: Once the best-fitting model is identified, assess whether it is a good model by examining the residuals (differences between observed and predicted values). If the residuals are randomly distributed and show no clear pattern, the model is likely a good fit for the data within the given scope.

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Key Concepts

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

Scatterplot

A scatterplot is a graphical representation of two variables, where each point represents an observation in the dataset. It helps visualize the relationship between the variables, allowing for the identification of patterns, trends, or correlations. In the context of modeling, analyzing the scatterplot is crucial for determining which mathematical model may best fit the data.
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Mathematical Models

Mathematical models are equations or functions that describe the relationship between variables in a dataset. Common types include linear, quadratic, logarithmic, exponential, and power models. Each model has distinct characteristics and is suitable for different types of data patterns, making it essential to choose the right model based on the observed trends in the scatterplot.
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Model Fit

Model fit refers to how well a chosen mathematical model represents the data. It can be assessed using various statistical measures, such as R-squared, residual analysis, or visual inspection of the scatterplot. A good model fit indicates that the model accurately captures the underlying pattern of the data, while a poor fit suggests that the model may not be appropriate for the dataset.
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Related Practice
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 Fares r = 0.953 (x = time in minutes, y = fare in dollars)

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Textbook Question

Dummy Variable Refer to Data Set 18 “Bear Measurements” in Appendix B and use the sex, age, and weight of the bears. For sex, let 0 represent female and let 1 represent male. Letting the response variable represent weight, use the variable of age and the dummy variable of sex to find the multiple regression equation. Use the equation to find the predicted weight of a bear with the characteristics given below. Does sex appear to have much of an effect on the weight of a bear?


Female bear that is 20 years of age

Male bear that is 20 years of age

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Textbook Question

Finding the Best Model

In Exercises 5–16, construct a scatterplot and identify the mathematical model that best fits the given data. Assume that the model is to be used only for the scope of the given data, and consider only linear, quadratic, logarithmic, exponential, and power models.

Detecting Fraud Leading digits of check amounts are often analyzed for the purpose of detecting fraud. The accompanying table lists frequencies of leading digits from checks written by the author (an honest guy).

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Textbook Question

Interpreting a Graph The accompanying graph plots the numbers of points scored in each Super Bowl from the first Super Bowl in 1967 (coded as year 1) to the last Super Bowl at the time of this writing. The graph of the quadratic equation that best fits the data is also shown in red. What feature of the graph justifies the value of R^2 = 0.205 for the quadratic model?

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Textbook Question

Sum of Squares Criterion In addition to the value of another measurement used to assess the quality of a model is the sum of squares of the residuals. Recall from Section 10-2 that a residual is (the difference between an observed y value and the value predicted from the model). Better models have smaller sums of squares. Refer to the U.S. population data in Table 10-7.

a. Find the sum of squares of the residuals resulting from the linear model.

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Textbook Question

Finding the Best Model

In Exercises 5–16, construct a scatterplot and identify the mathematical model that best fits the given data. Assume that the model is to be used only for the scope of the given data, and consider only linear, quadratic, logarithmic, exponential, and power models.

Population Growth Here are the values of the world population (billions) beginning with the year 2000:

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