Tool Set for Improving Transactional Processes

Hi, questions for those of you who have plenty of down-to-earth, hands-on experience applying six sigma to transactional processes:

Our experience as well as input from colleagues in other industries indicates that some of the statistical tools are not really applicable for achieving the desired improvements in transactional processes.

The tools we find most useful are: Project Definition and Scoping, Process Mapping, C&E Matrix, FMEA and Control Plans.

The tools we find, over and over again, are not useful are statistical tools i.e., Hypothesis tests, Regression and Design of Experiments.

We are curious about the experiences of other organizations. Is there a lot of value in teaching some of the statistical tools mentioned above for transactional processes?

Are there other tools, within each of the MAIC phases that some of you have found immensely helpful in identifying solutions. If yes, then, which are those tools?

In our classes, although we have taught hypotheses test, DOE and other advanced statistical tools, we find that our transactional Belts just do not apply them because they do not see value in transactional processes.

All insights are welcome. Thanks.