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rams replied to the topic Six Sigma – attacking variation or mean and variation in the forum General 12 years, 5 months ago

rams replied to the topic sample size in the forum General 19 years, 2 months ago
tony,
here’s a simple formula for type I error = 5% and type II error=5% (ie, power = 95%):
n = 121/lambda^2
lambda is sigma fold, usually from 2 to 4. if let’s say, you choose lambda=2.72, that means, you want to detect a change in sigma as much as 2.72 times with a false detection rate of 5% (type I) and a missed detection rate of 5% (type…[Read more] 
rams replied to the topic Normal data for control charting??? in the forum General 19 years, 2 months ago
Also, that is why we use Xbar charts to achieve normality of data by invoking the central limit theorem.

rams replied to the topic Games to illustrate DMAIC in the forum General 19 years, 3 months ago

rams replied to the topic DoE Design For Multi Level Factors? in the forum General 19 years, 4 months ago
Maybe this is an alternative:
If in case you are not really sure if there are quadratic effects, then try a 2×2 using the low and high levels of your factors.
Check for lack of fit or validate runs on the midpoints to check for curvature.
If no significant curvature, then the experiment is OK.
Else, augment the design to form a central…[Read more] 
rams replied to the topic Statistical Control and DOE in the forum General 19 years, 4 months ago
I always stress this point during my DOE training… before you collect data for experiments, make sure process is in control. I illustrate this using the “catapult.”
I shoot the ball using a low and high start angle and record the data. Participants are surprised that the lower angle produced a longer distance. This is not logical.
It’s because…[Read more] 
rams replied to the topic What is the benefit of Rolled Throughput Yield (RTY) in the forum General 19 years, 5 months ago
RTY simply means the proby of manufacturing a defect free unity. it’s up to you if this metric is important to u and to your company as well.

rams replied to the topic BoxCox transformation on Minitab in the forum General 19 years, 10 months ago
try reading this article from Thomas Pyzdek.
Has anyone use the Johnson Curves ?
http://www.qualitydigest.com/dec99/html/nonnormal.html 
rams replied to the topic Goodnesss Of Fit in the forum General 19 years, 10 months ago

rams replied to the topic Example of Variation in the forum General 19 years, 10 months ago
Ask the students to write 5 capital letter “A”s. Next, instruct them to write 5 more As, this time using the other hand.
Here’s how you explain it:
Imagine you are a company producing capital letter As. How long have you been producing these As, or in other words, how long have you been writing these As? The estimate should be around 20 to 25…[Read more] 
rams replied to the topic What is the highest index of Cpk? in the forum General 19 years, 10 months ago
You can also take a look at your gage resolution. Your equipment might not be capable of detecting changes in measurements.

rams replied to the topic Games used in Teaching FMEA in the forum General 19 years, 10 months ago
I have attended one FMEA training and it uses building blocks for exercise.
The objective is to build a car using the building blocks following some specifications, like, weight, length, height and functionality.
We would then develop a design FMEA on the car we built.

rams replied to the topic should cpk always lesser than ppk in the forum General 19 years, 10 months ago

rams replied to the topic DOE P values in the forum General 19 years, 10 months ago
Just don’t forget to use good engineering judgement, prior knowledge and common sense when assessing the importance of each effect.
rams 
rams replied to the topic Paired ttest p value in the forum General 19 years, 10 months ago
CT,
When you jumble the arrangement, you don’t get the same difference of each pair. In this way, result will be different.
If you use 2sample ttest (2 independent) samples, you’ll get the same result. 
rams replied to the topic Capability Analysis in the forum General 19 years, 10 months ago
Some references state that for onesided spec, Cp=Cpk. Some references state it does not exist. I prefer the second since Cp measures how potentially you are capable of meeting requirements, and requirements refer to your specification range (only applies to 2 sided spec).
rams 
rams replied to the topic Mid points in DOE in the forum General 19 years, 10 months ago
Great discussion guys.
Same thought as Eileen, I recommend adding midpoints to test for nonlinearity. Should there be evidence that the effect is nonlinear, then just add the “axial” points to complete a central composite design.
rams 
rams replied to the topic Paired ttest p value in the forum General 19 years, 10 months ago
When performing this test, maintain the order of the data because they are “paired” (not independent). Else, you are performing a 2sample test where the assumption is that the 2 population are independent. Paired ttest is like performing a one sample test on the difference of each paired data. Your null hypothesis is Ho : difference = 0.
Hope…[Read more] 
rams replied to the topic Probability analysis in the forum General 19 years, 10 months ago
Agree that hypergeometric is used in this situation.
But what if you apply it to high volume production with let’s say a lot size of 5000 and above? I had problems using the hypergeometric function in the excel software as it is somewhat limited to a certain factorial value (hypergeometric uses the factorial function).
My solution ? For very…[Read more] 
rams replied to the topic Sample Size requirement for Cpk in the forum General 19 years, 11 months ago
Ross,
thank you so much. let me know once you have the details.
Rick,
thanks for the info. will purchase the book ASAP.
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