Some of the causes can namely affect the controlled quality characteristic with time leg and
it can evocate problems with assigning the indicator values to the values of sample statistics
computed from the output quality characteristic values.
The analysis of the particular indicators in the frame of the assignable cause identification
must be spread to (using regression and correlation analysis, DOE) in the situation when
there exists important correlation between indicators and their joint could have an
significant influence on the quality characteristics values.
The forth variant represents the combination of variants I and III.