QW5 Help Files
The Relationship screens are a very useful way of directing QW to take advantage of known relationships between variables. It is not always the variable which is highlighted with a rule violation that is the cause of a problem.
QW 5.0 automatically calculates the relationships between one variable and ALL of the others, and displays the results from largest to smallest. QW tests these relationships and will highlight any relationships which have strong statistical evidence that they are correlated. This is a very powerful tool in determining the cause of an upset and also allows you to build on the knowledge of the process as new relationships are discovered.
Understanding this Screen
The number displayed on the chart is not the correlation coefficients but the squared value of the coefficient. By squaring this number it causes a value that states the percentage of variation in one variable that is explained by another. If a strong relationship is detected, using the T-test, the value will be highlighted to bring your attention to it. If it is not highlighted there was no statistical evidence to support the relationship and you should ignore it.
A positive percentage indicates that two variables are moving together in the same direction some part of the time. A negative number indicates the variables are moving in opposite directions.