Provides a graphical means for assessing and communicating the relationship between two (or possibly three) variables.
|When to Use||Purpose|
|Start of project||Assists in developing alternatives measurement systems in cases where a variable is difficult or expensive to measure - you can use highly correlated and logically linked alternative variables as substitute variables.|
|Mid-project||The first rule of data analysis is to graph the data before running any statistical tests. Use scatterplots along with any statistical tool that tests for relationships between variables, such as regression.|
|Mid-project||Assess if an input (X) has a strong relationship with an output (Y) to help eliminate noncritical X's from consideration.|
|Mid-project||Evaluate two inputs to eliminate inputs that duplicate the same information (for example, inputs of Degree Obtained and Years of School are likely to explain the same variation of the output). This case is common in multiple regression with many variables.|
|End of project||If used earlier as part of the validation of the measurement system, it should be reapplied to the improved process to again validate the measurement system.|
Two numeric variables (both can be continuous or discrete), with optional categorical variables.