Notes and Considerations
Montgomery CH03 Example 3.13 p. 139
Output, along with R script, is included in the file "CH03 Example 3-13 manage autocorrelation with additional predictor.docx" attached below.
Example of how, in some situations, adding another predictor (explanatory variable) to a linear model can reduce autocorrelation in the model residuals.
Also includes comparison of R functions for checking autocorrelation using Durbin-Watson
Shows possible inconsistency of durbinWatsonTest() function (car package) and provides an alternative using the 'dwtest()' function from the lmtest package.
Data Set
Tables 3.13 & 3.15 soft drink concentrate sales data
See file "DATA Montgomery TS data for chapter examples.xlsx" at the bottom of page Introduction to Time Series Analysis and Forecasting (Montgomery)
Data is also included in the R script file attached below.
Analysis or Script File
See the file "CH03 Example 3-13 manage autocorrelation with additional predictor.R" attached below.