rams

Dear Sensei,

Thank you for clarifying the difference between variation and variance. So if a process is precise but not accurate, in six sigma parlance this would still be called variation. Got it.

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]

Also, that is why we use Xbar charts to achieve normality of data by invoking the central limit theorem.
 

You can use the catapult in the entire DMAIC. You can use it as an exercise for : Process Mapping, Gage R&R, Capability Study and Variation Study, DOE, and Control Charting.
It’s very effective as students can relate all exercise and be able to appreciate the DMAIC process.
 

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]

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]

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.

try reading this article from Thomas Pyzdek.
Has anyone use the Johnson Curves ?
http://www.qualitydigest.com/dec99/html/nonnormal.html

there is no restriction on sample size as long as no more than 20% of your “cells” have an expected value of less than 5. This is a warning you get when you use SAS JMP (not sure for other software).

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]

You can also take a look at your gage resolution. Your equipment might not be capable of detecting changes in measurements.

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.
 

Hemanth,
Now I am confused :-).
I thought Cpk computation is based on “within subgroup” variation because of R-bar.
Enlighten me.
rams

Just don’t forget to use good engineering judgement, prior knowledge and common sense when assessing the importance of each effect.
rams

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 2-sample t-test (2 independent) samples, you’ll get the same result.

Some references state that for one-sided 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

Great discussion guys.
Same thought as Eileen, I recommend adding midpoints to test for non-linearity. Should there be evidence that the effect is non-linear, then just add the “axial” points to complete a central composite design.
rams

When performing this test, maintain the order of the data because they are “paired” (not independent). Else, you are performing a 2-sample test where the assumption is that the 2 population are independent. Paired t-test is like performing a one sample test on the difference of each paired data. Your null hypothesis is Ho : difference = 0.
Hope…[Read more]

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]

Ross,
thank you so much. let me know once you have the details.
Rick,
thanks for the info. will purchase the book ASAP.
Rams