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Review Homework. Residuals. From the Carnegie Foundation math.mtsac.edu/ statway /lesson_3.3.1_version1.5A. Residual (or error). Observed y MINUS predicted y. Analyzing Residuals. Determines the effectiveness of the regression model. Residual Plots.
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Residuals From the Carnegie Foundation math.mtsac.edu/statway/lesson_3.3.1_version1.5A
Residual (or error) • Observed y MINUS predicted y
Analyzing Residuals • Determines the effectiveness of the regression model
Residual Plots • A scatterplot of Residuals vs. X
Residual Plots Determine • If it the model is appropriate, then the plot will have a random scatter. • If another model is necessary, the plot will have a pattern. Pattern = Problem
Examples Determine, just by visual inspection, if the linear model is appropriate or inappropriate.
The only way to know is to see the residual plot. 1. Does their appear to be a pattern in the residual plot? Yes, quadratic. 2. Does this support your original guess? You must now see that a linear model does NOT fit this data.
The only way to know is to see the residual plot. 1. Does their appear to be a pattern in the residual plot? Yes, it fans out as x increases. 2. Does this support your original guess? You must now see that a linear model does NOT fit this data.
The only way to know is to see the residual plot. 1. Does their appear to be a pattern in the residual plot? Yes, it looks quadratic. 2. Does this support your original guess? This was very tricky. The scale was very small. You must now see that a linear model does NOT fit this data.
The only way to know is to see the residual plot. 1. Does their appear to be a pattern in the residual plot? Yes, it seems decrease as x increases. 2. Does this support your original guess? This was tricky. You must now see that a linear model does NOT fit this data.
Example: Calculate ResidualTracking Cell Phone Use over 10 days
Example: Calculate ResidualTracking Cell Phone Use over 10 days
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