Lesson 4 (N) How wil the line fits the data - Copy

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Pennsylvania State University *

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MISC

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Statistics

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May 1, 2024

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docx

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7

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Chapter 3 Describing Relationships Lesson 4 How well the line fits the data 1. Determining if a linear model is appropriate: Residual Plots; 2. The Standard Deviation of the Residuals ; 3. The coefficient of Determination . 1. Determining if a linear model is appropriate: Residual plots help us assess whether or not a linear model is appropriate. Example 1: A scatterplot shows the relationship between the number of hours studied the night before a test and score for the test.
The line seems to be a good fit for this relationship. The residuals look randomly and evenly scattered around the line. We can’t see any obvious curved pattern in the residual plot. Example 2: The least-squares regression line clearly doesn’t fit this association very well!
This U-shaped pattern in the residual plot indicates that the linear form of our model doesn’t match the form of the association. A curved model might be better in this case. https://savi-cdn.macmillantech.com/brightcove/index.html? videoId=5731634971001 To determine whether the regression model is appropriate, look at the residual plot. If there is no curved pattern in the residual plot and the residuals are evenly scattered above and below the line, the regression model is appropriate. If there is a curved pattern in the residual plot, consider using a regression model with a different form. Example 3: Is a linear model appropriate to describe the relationship between the weight (in carats) and price (in dollars) of diamonds with excellent cuts? Interpretation: The linear model relating price to carat weight is not appropriate because there is a U- shaped pattern in the residual plot. 2. The Standard Deviation of the Residuals:
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