Dr. Dave Stimley
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Dr. Dave Stimley replied to the topic Where to begin? in the forum General 18 years, 12 months ago
Try some basic observational studies of the various gurus to see which produces the best results. ANOM – Analysis of Means is an excellent method for accomplishing this. Next, incorporate these best practices into a proceedure. Bring this procedure into a state of statistical control. Then improve it if necessary or move on to the next pr…[Read more]
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Dr. Dave Stimley replied to the topic Transforming Non-normal Data in the forum General 19 years, 6 months ago
The best way of handling non-normal data when doing a capability study is to use a Pearson transformation which looks at the percentiles in the tails based on skewness and kurtosis and then gives the equivalent Cp and Cpk values. (Reference Quality Progress – Sept. 1989). This is also done automatically if using statistica software. In any case…[Read more]
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Dr. Dave Stimley replied to the topic Calculations of Yield, Sigma Level and Cpk in the forum General 19 years, 6 months ago
Use these formulae: RTY= e^-(Sum of DPU) or -ln(RTY) = Sum of DPUs whichever is more convienient.
Then DPMO = (Sum of DPUs*1000000)/sum of OE’s
Then Convert your DPMO’s to Sigma.
To get to Cpk: Once you know DPMO, Take the DPMO value and divide it by 2 then find the Z value from a Z table. For Example, 2700DPMO/2 = 1350DPMO or as a fra…[Read more] -
Dr. Dave Stimley replied to the topic What about STATGRAPHICS ? in the forum General 20 years, 2 months ago
Yes – I used to work for Motorola, used Statistica there as well.
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Dr. Dave Stimley replied to the topic When to use Cpk or Cp to determine the six sigma value? in the forum General 20 years, 5 months ago
Here is how it is done:
You will need the values of CPU and CPL to start.
Then:
1. Compute Zu = 3xCpu and Zl = 3xCpl
2. Find the fraction defective for each of the Z values from a Z table and add them together.
3. Multiply step 2 by 1,000,000 to get equivalent DPMO
4. From the DPMO you may find the sigma from a conversion table or…[Read more]