A simple regression tool used to plot one Y versus one X to evaluate linear, quadratic, or cubic relationships. The best fit regression line is displayed with optional confidence and prediction intervals around the fitted regression line. The confidence interval is for the regression equation and the prediction interval is for the individual points.
|When to Use||Purpose|
|Start of project||Compare a proposed or existing gage to a highly qualified device (such as a certified lab). A high r-squared (R-Sq) value provides reasonable certainty of the test gage matching the reference gage.|
|Start of project||Use to help develop alternative measurement systems for cases in which a variable is difficult or expensive to measure. Use highly correlated and logically linked alternative variables as substitute variables.|
|Mid-project||Investigate the relationship between a process input and the process output to help decide to either keep the input as a potential leverage variable or set it aside as most likely not important.|
|Mid-project||Evaluate two inputs to identify whether they duplicate the same information. For example, inputs of Degree Obtained and Years of School are likely to explain the same variation of the output, so one of them can be eliminated. This is used primarily in multiple regression analysis with many variables.|
|End of project||Verify the measurement system. If you use a fitted line plot earlier as part of the validation of the measurement system, create another one with the improved process to again validate the measurement system.|
Continuous Y with one continuous or discrete X (with multiple levels)