ISO9000 and TS16949 (auto industry) defines systems that need to be in place in order to ensure high quality designs, processes, and production. This includes management responsibilities, design systems, purchasing, document control, auditing, corrective actions, etc… Just one of these areas is continuous improvement.
Six Sigma is a method of…[Read more]
Pooled Var = [V1(n1-1) + V2(n2-1) + V3(n3-1)] / [(n1-1) + (n2-1) + (n3-1))
You can think of this as a weighted average of the variances … weighted using the degrees of freedom for each group. Of course, if the groups all have the same sample size, then the weighting is equal, and the pooled variance is simply the mean of the va…[Read more]
The problem with using the same parts for both studies is that the linearity parts are typically hand-selected so that the parts filled the expected operating range. These parts can’t provide an estimate of the process variation.
The GR&R parts, on the other hand, should be randomly selected hoping to provide a good representation of the…[Read more]
“If we did the PPAP’s and got the capability and controls that we pretend to, hardly any of this would be necessary.”
If “we” were able to do that, none of US would be necessary as problem solvers, now would we…
Fact is, PPAP’s are usually just a list of items to check off, and the “meat” of what underlies each of those check…[Read more]
There is a lot of confusion about the binomial distribution in this thread.
The binomial distribution involves the random variable x, where x is number of “successes” from n trials where each trial involves a probability of success equal to p.
The potential values of x are 0, 1, …, n, and the binomial distribution gives the values for each of…[Read more]
1. When they say 95% reliability, they are talking about the lifespan at which 5% of the units are expected to have failed (95% survive). This is the 5th percentile for the distriubution of expected lifespans (in cycles, in your case).
2. When they say “at 90% confidence” they are usually referring to the 90% lower confidence limit for the 5th…[Read more]
The AIAG Measurement System Analysis Reference Manual calls for at least 5 parts whose measurements cover the operating range of the gage, and then to measure each part at least 10 times by an operator who normally uses the gage.
Word Mark: STATAPULT
Goods & Services: IC 009. US 021 023 026 036 038. G & S: SCIENTIFIC AND TEACHING APPARATUS COMPRISED OF WOOD AND RESEMBLING A CATAPULT FOR USE IN DEMONSTRATING AND TEACHING MATHEMATICAL CONCEPTS, PROCESSES, METHODS, AND CAUSE AND EFFECT, AND FOR CONDUCTING MATHEMATICAL MODELING EXPERIMENTS. FIRST USE: 19891231. FIRST USE IN…[Read more]
Doc replied to the topic Sigma 17.4 with N=33. What is the standard deviation in the forum General 16 years, 11 months ago
Mean +/- Z[(c+1)/2]*Sigma/SQRT(n)
Where Z[(c+1)/2] is the 100*(c+1)/2th percentile of the standard normal distribution and c is the confidence, such as 83.3. By the way, Z[(c+1)/2] is the same as Z[1-(alpha/2)]
So, you look up Z[(.833+1)/2]=Z(0.9165) in a standard normal table and you find 1.38. This is the value of z for which 91.65%…[Read more]
I’m not sure where he got 2% and 8%.
I suspect these are mutated acceptance criteria taken from the 10%^2=1% and 30%^2=9% metrics I mentioned in the earlier post. These are calculated using the AIAG MSA Reference Manual acceptance criteria for %GRR and %Tolerance.
Some people have rounded the 9% up to 10% for ease-of-use/presentaiton.
Careful here … you are mixing up on the indices.
The AIAG MSA Reference Manual uses the following accpetance criteria for %GRR and %Tolerance. Note that these are standard deviation-based metrics:
<10% – generally acceptable
10%-30% – may be acceptable based upon importance of application, cost of measurement device, cost of repairs,…[Read more]
Go to the Minitab Help.
Click on the help for Graphical Summary. Select “see also”. Select “Methods and formulas”. Scroll down to find the formulas you’re seeking. The form for the median is not as simple as that of the mean. Read up on it though.
n people have just finished eating at a Chinese restaurant and the waiter gives them n fortune cookies on a single plate in the center of the table.
One person picks up the plate, chooses one of the cookies, and then passes the plate to the next person.
That person chooses one of the remaining cookies, and then passes the plate to the next…[Read more]
It would be good form to say something like “Six Sigma is a registered trademark of Motorola, Inc.”, BUT you certainly don’t need permission to use it in an article.
I have heard some rumors that Motorola has been known to contact some companies using the term “for profit”, possibly discussing licensing of the trademark, but haven’t gotten…[Read more]
Consider Statistical Methods for Reliability Data by Meeker & Escobar. This book is more focused on the analysis of reliability data.
O’Connor’s book is more focused on how to setup engineering and management systems that result in reliable products, though it does cover some basic analysis techniques.
Also consider the on-line resource…[Read more]
Stan & RubberDude – Here is an acronym translation:
DFSS – Design for Six Sigma
DMEDI – Define, Measure, Evaluate, Design, Integrate (similar to DMAIC, but applies to DFSS instead)
QFD – Quality Function Deployment – used to help determine CTQ’s
CTQ – Critical to Quality characteristics – highest priority benefits the customer is looking for…[Read more]
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