Regression Lab In StatCrunch - Revision history

Carver at 18:06, 17 February 2019

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 '''Lab 3: Regression, Correlation and Outliers
-* We are going to work with the small diamonds data set again: [[Media:diamonds3K.xlsx|diamonds3K]] sampled from a larger data set with [http://ggplot2.tidyverse.org/reference/diamonds.html Codebook].
+* We are going to work with the small diamonds data set again, accessible here: [[Media:diamonds3K.xlsx|diamonds3K]] sampled from a larger data set with [http://ggplot2.tidyverse.org/reference/diamonds.html Codebook].
 * We are going to look at the three dimensions of diamonds and how they covary: length (x), width (y), and height (z).
 * Make a scatter plot for (x versus y) and separately for (x versus z).

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 * Can you tell if the data were recorded wrong or if the diamond really had those dimensions?  Consider what x, y, and z mean and remember you also have a measure of the diamond's weight (carat). Plot scatter plots with carat and x, y or z, and '''discuss'''.
 * '''Repeat for the other most extreme outliers.'''
-* Plot the Residuals versus X-Values, a histogram of the residuals, and a QQ-Plot of the residuals. '''Where does the outlier(s) show up? With the outliers removed, is a simple-linear regression analysis appropriate?'''
+* Plot the Residuals versus "X-Values" (explanatory variable), a histogram of the residuals, and a QQ-Plot of the residuals. '''Where does the outlier(s) show up? With the outliers removed, is a simple-linear regression analysis appropriate?'''
 * '''Report the correlation coefficient and regression line with the outliers and without the outliers (see below).'''
 * To do the analyses without the outliers, use Stat, Regression, Simple Linear to Save Residuals, then use a "where" function to restrict the data to points with small enough residuals.

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 * Click on an outlier to turn it pink.
 * '''Is the outlier an outlier for the ''other'' relationship? (x versus y) versus (x versus z)'''.  The dot on the other scatter plot also turns pink.
-* Look at the row in the data set for each outlier.  Press one of the arrows on the pink box that appeared on the lower left.
+* Look at the row in the data set for each outlier.  To find the row, press one of the arrows on the pink box that appeared on the lower left.
 * Can you tell if the data were recorded wrong or if the diamond really had those dimensions?  Consider what x, y, and z mean and remember you also have a measure of the diamond's weight (carat). Plot scatter plots with carat and x, y or z, and '''discuss'''.
 * '''Repeat for the other most extreme outliers.'''

@@ Line 7: / Line 7: @@
 * Click on an outlier to turn it pink.
 * '''Is the outlier an outlier for the ''other'' relationship? (x versus y) versus (x versus z)'''.  The dot on the other scatter plot also turns pink.
-* Look at the row in the data set for each outlier.
+* Look at the row in the data set for each outlier.  Press one of the arrows on the pink box that appeared on the lower left.
 * Can you tell if the data were recorded wrong or if the diamond really had those dimensions?  Consider what x, y, and z mean and remember you also have a measure of the diamond's weight (carat). Plot scatter plots with carat and x, y or z, and '''discuss'''.
 * '''Repeat for the other most extreme outliers.'''

@@ Line 8: / Line 8: @@
 * '''Is the outlier an outlier for the ''other'' relationship? (x versus y) versus (x versus z)'''.  The dot on the other scatter plot also turns pink.
 * Look at the row in the data set for each outlier.
-* Can you tell if the data were recorded wrong or if the diamond really had those dimensions?  Consider what x, y, and z mean and remember you also have a measure of the diamond's weight (carat). Plot scatter plots with carat and '''discuss'''.
+* Can you tell if the data were recorded wrong or if the diamond really had those dimensions?  Consider what x, y, and z mean and remember you also have a measure of the diamond's weight (carat). Plot scatter plots with carat and x, y or z, and '''discuss'''.
 * '''Repeat for the other most extreme outliers.'''
 * Plot the Residuals versus X-Values, a histogram of the residuals, and a QQ-Plot of the residuals. '''Where does the outlier(s) show up? With the outliers removed, is a simple-linear regression analysis appropriate?'''
 * '''Report the correlation coefficient and regression line with the outliers and without the outliers (see below).'''
 * To do the analyses without the outliers, use Stat, Regression, Simple Linear to Save Residuals, then use a "where" function to restrict the data to points with small enough residuals.

@@ Line 13: / Line 13: @@
 * Plot the Residuals versus X-Values, a histogram of the residuals, and a QQ-Plot of the residuals. '''Where does the outlier(s) show up? With the outliers removed, is a simple-linear regression analysis appropriate?'''
 * To do the analyses without the outliers, use Stat, Regression, Simple Linear to Save Residuals.
-* Then use a where function to restrict the data to points with small enough residuals.
+* Then use a "where" function to restrict the data to points with small enough residuals.

@@ Line 11: / Line 11: @@
 * '''Repeat for the other outliers.'''
 * '''Report the correlation coefficient and regression line with the outliers and without the outliers.'''
-* Plot the Residuals versus X-Values, a histogram of the residuals, and a QQ-Plot of the residuals. '''Where does the outlier(s) show up? With the outliers removed, is regression appropriate?'''
+* Plot the Residuals versus X-Values, a histogram of the residuals, and a QQ-Plot of the residuals. '''Where does the outlier(s) show up? With the outliers removed, is a simple-linear regression analysis appropriate?'''
 * To do the analyses without the outliers, use Stat, Regression, Simple Linear to Save Residuals.
 * Then use a where function to restrict the data to points with small enough residuals.