Hi, I understand process capability for variable data. What happens when you calculate process capability for attribute data? In many cases the attribute data may refer to a one sided specification limit only, so converting the DPMO to a Z level and then an equivalent Cp or Pp seems erroneous. One of the books I read said that process capability for attribute data should be defined in terms of the CL of the relevant attribute control-chart (c, n..)? Why do we bother to convert Cp and Pp to Sigma levels? Why not just work with Cp or Pp? How does the timming of the data collection influence the calculation? I get the impression that if I've collected long-term data the sigma calculator assumes a 1.5 sigma shift and then corrects it for the shift to give me an equivalent short-term sigma ratting. What if I've corrected the process and I want to predict the future sigma ratting?
forrestbreyfogle 10/17/2004
POSTING: Thank you both for your prompt and professional inputs, I truly appreciate it. You both recommend stream map, is this a process mapping exercise where value-added processes are eliminated?
RESPONSE: There is more to value stream mapping than just a "mapping exercise where value-added [assume you mean non-value-added] processes are eliminated."
Assessing the 30,000-foot-level metric outputs for organizational value streams can be very beneficial. When these metrics (e.g., WIP and cycle time) are unsatisfactory this pulls for the creation of a Six Sigma/Lean project. When this occurs, we would first consider the application of Lean tools such as a detailed value stream analysis to identify and resolve waste issues.
Hope this helps. For more information you can contact me directly.
Forrest Breyfogle
512-918-0280
forrest@smartersolutions.com
www.smartersolutions.com
csantiago 10/14/2004
Thank you both for your prompt and professional inputs, I truly appreciate it. You both recommend stream map, is this a process mapping exercise where value-added processes are eliminated?
forrestbreyfogle 10/13/2004
INITIAL POSTING: Hello! I am a BB currently on my 3rd project. Our company undertakes clinical laboratory tests (service), and my boss just asked me to work on a new project which is quite differeent. The consumer division just submitted a quote for a project which was the lowest among the competitors, and consequently won the tender. The problem is that our Regional Mgr thinks they have gone over-board with this bid in an effort to get the contract. My boss wants me to see if their bid is realistic and if the consumer division has room for improvement. Can anyone give me any inputs as to what to measure? I'm thinking re-works, or total cost / project?Thanks. Renato
RESPONSE: I suggest that start tracking the output of your overall process at the 30,000-foot-level. This could be some measure of profit for each project that you undertake. Would go as far back in time as reasonable. Project size and differences could be considered common cause variability. If the process is in-control/predictable you could combine the data via a probability plot to make a statement about its process capability/performance. Within this assessment you could see how this latest project compares to past projects.
To address overall improvement needs you could then proceed taking this on as a Six Sigma/Lean project. One of the tools that should be most beneficial for this project is a value stream map.
Upon project completion the 30,000-foot-level measurement can be used to illustrate/determine project value.
Hope this helps. Please let me know if you would like to discuss further.
Forrest Breyfogle
forrest@smartersolutions.com
512-918-0280
www.smartersolutions.com
mehryarsalim 10/13/2004
First, map the process to make sure you capture all the details and process flow. Second, be realistic with your estimates and targets. Third, be aware of potential "soft savings" associated with the project. This could range from customer retention to company reputation to improving your bidding process. Make sure you estimate the benefits associated with such savings.
The current and future state process charts / value stream maps will give you a good picture of where you currently stand and where you want to be in order to improve your process and make any profits from this project. Measurements could range from defects, re-works, cycle times, lead times, etc.