The standard deviation is a measure of variation, usually applied to normal distributions, although it is also defined to be the square root of the second moment of any distribution.
The standard deviation is simply the square root of the variance. They are one-one. For some circumstances, such as linear combinations of normal variates, the…[Read more]
Also check out this Quality Digest Article:
My own favorite reference for DOE continues to be Douglas Montgomery’s “Design and Analysis of Experiments”. A very well written text – and well received by the statistical community.
Here are a few web sites that might help:
NIST/Sematech Engineering Statistics Handbook:http://www.itl.nist.gov/div898/handbook/index.html
Statistical DOE…[Read more]
In response to Ravi’s comments (shown in bold):
1) GRR number shall always be looked in reference to the tolerance. Ultimately what matters is the ability of the gage to resolve a tolerance.
I have to cordially disagree. There are many occasions when the gage is used to take measurements for process improvement activities, such as DOE’s. In…[Read more]
I should have mentioned that the AIAG MSA reference manual clearly prefers the metrics based upon the production variation over those based upon the tolerance.
I quote from the chapter titled “MEASUREMENT SYSTEM DISCRIMINATION”:
“Thus a recommendation for adequate descrimination would be for the apparent resolution to be at most one-tenth of…[Read more]
The same criteria applies when using process variation in the denominator. The AIAG MSA reference manual says:
“Acceptability Criteria – The criteria as to whether a measurement system is satisfactory are depnedent upon the percentage of part tolerance or the manufacturing production process variability that is consumed by measurement system…[Read more]
It seems you could do a combination of both.
You can learn a lot about problem solving, FMEA, process capability, and control charting just from the internet and via books. The MSA, FMEA, & SPC reference manuals from AIAG:(http://www.aiag.org/publications/quality/dcxfordgm.html)
provide a wealth of information for only $38!!
Find out what…[Read more]
I myself don’t see those costs as too outrageous, depending on what exactly the consultant does. The GB should easily recoup those costs fairly rapidly.
I don’t see the GB, BB, & MBB as a “caste” system. In my business these labels are used to provide and easy/quick identification of person’s level of skill and experience. BB’s are expected to…[Read more]
Six Sigma methods are applicable to all industries and service organizations.
This web site provides a good start. You can do searches using http://www.google.com to find details on specific methods. For statistics I tend to prefer this link:
For FMEA try
For SPC, MSA, and FMEA…[Read more]
Have you seen Pyzdek’s book? If so, how do you think it compares to Breyfogle’s and Harry’s books?
Those three seem to be the most often referenced Six Sigma books.
Most reviews suggest Breyfolgle’s Implementing Six Sigma is the most usable guide to Six Sigma, from a tools standpoint. Would you agree?
OK, get ready for a long equation that I use in Excel. It is accurate to two decimal places between 3.2 and 9 Sigma, and to one decimal place between 2.5 and 3.2 Sigma. It should not be used below 2.5 Sigma or above 9 Sigma (were you that lucky).
Sigma equals . . .…[Read more]
Ken K. replied to the topic What alpha value given importance than the beta value in the forum General 18 years, 10 months ago
The beta risk is most certainly considered and minimized IF the testing is set up correctly. The beta risk is minimized by using proper sample sizes.
Before any data are collected you need to consider the minimum samples sizes required for the analysis that will be used. The maximum acceptable beta and alpha are both involved in the calculation…[Read more]
GT is correct.
By manufacturing several (3) bonds without changing the equipment settings, there is an assumption made that these three bonds are nearly identical. Of course the variation measurement you obtain will actually be the combination of measurement variability PLUS part-to-part variability for very similar parts. There is really no way…[Read more]
What KMB and Dave are saying is . . .
If the p-value for a correlation coefficient test is less than 0.05, it indicates that the correlation coefficient IS significantly different from zero (either positive or negative) at the alpha = 0.05 level.
This means that there is some significant amount of linear relationship between your two variables…[Read more]
Please post a link, or at least reference a text or journal article that describes what you call “variable search”. Your posts haven’t given much of a clue as to what, specifically, you are talking about.
I have been using designed experiments for over 15 years and have only heard the term used in the sense of the use of fractional…[Read more]
Motorola still owns the Six Sigma trademark, but unlike Mikel Harry, has been kind enough to allow others to use its trademark without seeking legal action.
Though there seems no tendency to do so, Motorola still has every legal right to demand the “Six Sigma” community stop using its trademark.
On the other hand, Mike Harry tried to…[Read more]
The nicest way I’ve seen is to related the standard deviations to the lengths of the sides of a right triangle.
The length of the hypotenuse is equal to the square root of the sum of the squared side lengths.
Clearly the length of the hypotenuse can’t be simply the sum of the side lengths – that just wouldn’t make sense from a visual…[Read more]
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