Calling All SMEs
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 This topic has 23 replies, 11 voices, and was last updated 15 years, 5 months ago by Cravens.

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April 13, 2007 at 5:32 pm #46733
Dearest SMEs,
Can you provide me with a reference or general idea behind the importance of degrees of freedom? Definitions I have, general understanding as to how it affects my statistical outcomes I do not…..thanks!
F table….how to use and interpret it once I have the f stat? I was raised as a pvalue baby and need enlightenment… Thanks again!0April 13, 2007 at 6:49 pm #154778
Allthingsidiot OParticipant@AllthingsidiotO Include @AllthingsidiotO in your post and this person will
be notified via email.DoF is always # of samples minus 1
F table:First F test means Fatness in contrast to T test which means centering.F test is used when 2 samples variances are equal .It means to test for difference in dispersion,we should calculate the critical value and the test statistic,then upon that we can either ” reject” or “fail to reject” the null hypothesis.
Hope it is OK now
0April 13, 2007 at 7:16 pm #154782
roadrage01Member@roadrage01 Include @roadrage01 in your post and this person will
be notified via email.F test likes normality.. alot. Or better said, F test is not robust to nonnormality in the least.
Degrees of freedom – How many different types does the test see. We teach that a minimum of 4 is required in order to use the test. Higher is better. It comes down to the noise in the process. With fewer degrees of freedom, there is more noise that is hidden among the “types” that the test sees.
Hope it helps.0April 13, 2007 at 10:57 pm #154788Thanks RR01,
It sounds like you are describing the number of distinct categories when you describe the DOF…is this correct and if so they are not synonomous, correct?0April 14, 2007 at 1:23 am #154789this trail is the best example of how degenerated this site has become. “ftest relates to fat distribution”, “degrees of freedom have to do with the noise in the process” … you have to really be an allthingsidiot (o) or have roadrage to come up with such utter nonsense … and what does “we” mean, … the totally clueless who failed their baby introduction to statistics … what clowns and bobos!
0April 14, 2007 at 2:08 pm #154791
Allthingsidiot OParticipant@AllthingsidiotO Include @AllthingsidiotO in your post and this person will
be notified via email.SS
You have stolen my explanation in the day light?A pretender and thief in one unque personality?this is really a great mixture.0April 14, 2007 at 7:09 pm #154799Yeah…not exactly what I was looking for….someone with a tad of grey matter want to weigh in here and point me in a direction in terms of references for f distributions….stan, doc, darth, bueller, bueller?
0April 14, 2007 at 7:27 pm #154800
qualitycoloradoParticipant@qualitycolorado Include @qualitycolorado in your post and this person will
be notified via email.Anon,I don’t know exactly what questions you are trying to answer, but there are some good free resources online that can help you with degress of freedom and the F table.For instance, this page from StatSoft’s statistical textbook discusses degrees of freedom: http://www.statsoft.com/textbook/sttable.html
… is this kind of reference material you are looking for?
Best regards,
QualityColorado0April 14, 2007 at 7:28 pm #154801
qualitycoloradoParticipant@qualitycolorado Include @qualitycolorado in your post and this person will
be notified via email.…fyi, the full “electronic statistics textbook: from StatSoft is available (for free!!!) at this website:http://www.statsoft.com/textbook/stathome.html
Best regards,
QualityColorado0April 14, 2007 at 7:35 pm #154802
qualitycoloradoParticipant@qualitycolorado Include @qualitycolorado in your post and this person will
be notified via email.… also, try searching the “Engineering Statistics Handbook” from the U.S. National Institute of Standards and Technology (NIST) , online (at no charge!!) at this link:http://www.itl.nist.gov/div898/handbook/
I looked quickly, and there are quite a number of references to degrees of freedom — you may find your answers there …
Best regards,
QualityColorado0April 14, 2007 at 7:40 pm #154803
QuallityColoradoParticipant@QuallityColorado Include @QuallityColorado in your post and this person will
be notified via email.… may also want to try the search engine on the Minitab statistics reference site (also free, even though the Minitab product is not):http://www.minitab.com/Resources/… quite a few hits for “degrees of freedom” … Best regards,
QuallityColorado0April 14, 2007 at 9:53 pm #154808
F test, dfParticipant@Ftest,df Include @Ftest,df in your post and this person will
be notified via email.The ftest as you know is based on a ratio of two variances. The idea is that if the variances come from the same population, the two sample estimates of the variances are equal to one (i.e. they are equal)
In the case of the variance estimate you can look at the degree of freedom as the number of sample points that can be varied freely when you know the variance. For example, if you have 5 data points and you know that your variance is lets say 20, once you know four data points your fifth data point can be calculated via algrebraic equations. The determination of degrees of freedoms become more complex with more complex designs.
Because you estimate the variances and the ratio of the variances follows an fdistribution you will reject the null hypothesis when the fvalue exceeds a critical value. This is in line with the framework of hypothesis testing in general. This critical value is dependent on the degrees of freedom of each of the two samples and the alpha value.
So if you estimate two variances, one with lets say 5 data points and the other with 7 data points, and you assume an alpha of .05 saying that they are equal you look up the critical value in the ftable and compare it against the value that your two samples show. The pvalue is the cumulative frequency at the point of your estimated ratio given the fdistribution with your specific degrees of freedom. So, you can either look at the pvalue or you can compare the calculated fvalue with the critical fvalue. I hope this helps.
0April 15, 2007 at 6:49 am #154812
Allthingsidiot OParticipant@AllthingsidiotO Include @AllthingsidiotO in your post and this person will
be notified via email.Excellent Elaboration,thank you
0April 15, 2007 at 9:37 pm #154816Anon,
SME is the Society of Manufacturing Engineers.
Degrees of Freedom in Engineering terms refers to Kinematic constraints.
Three dimensionally speaking an object has 6 degrees of freedom, 3 translational degrees and 3 rotational degrees.
I doubt your question is regarding the Theory of Exact Constraints, but you really should get your terminology right.0April 15, 2007 at 11:44 pm #154820
qualitycoloradoParticipant@qualitycolorado Include @qualitycolorado in your post and this person will
be notified via email.EZWeld,Interesting posting, but come on, cut the guy some slack — he DOES have his terminology right!!Yes, as you point out, while SME can indeed stand for the “Society of Manufacturing Engineers (in the U.S.), its morecommon meaning in industry (worldwide) in general is “subject matter experts”. It is quite common to list SMEs on a Six Sigma project charter, for instance.And, yes, while the term “degrees of freedom” does have a specific engineering meaning, it has a specific (and different) meaning in statistics, also — this stastical meaning will be one more commonly referred to in Six Sigma project.
Best regards,
QualityColorado0April 16, 2007 at 3:35 am #154824
qualitycoloradoParticipant@qualitycolorado Include @qualitycolorado in your post and this person will
be notified via email.Anon,Here is an another explanation for degrees of freedom:http://www.tufts.edu/~gdallal/dof.htm
Best regards,
QualityColorado0April 16, 2007 at 8:51 am #154832QualityColorado,
Your right, I didn’t even think about “Subject Matter Experts”.
Every time I see SME I think about Manufacturing Engineers.
0April 16, 2007 at 10:03 am #154834
Allthingsidiot OParticipant@AllthingsidiotO Include @AllthingsidiotO in your post and this person will
be notified via email.Another third concept for SMEs:Small & Medium Enterprice?
0April 16, 2007 at 12:06 pm #154838
roadrage01Member@roadrage01 Include @roadrage01 in your post and this person will
be notified via email.Yes, it would be distinct catagories.
0April 16, 2007 at 11:51 pm #154859Thanks to all…links were very helpful QC, along with clearing up the confusion on my acronym. CHeers.
0April 17, 2007 at 8:07 am #154866
Bower ChielParticipant@BowerChiel Include @BowerChiel in your post and this person will
be notified via email.In the UK the acronym SME can mean Small to Medium Enterprise with reference to the size of a business/company!Bower Chiel
0April 19, 2007 at 4:01 pm #154988
roadrage01Member@roadrage01 Include @roadrage01 in your post and this person will
be notified via email.Anon, another example of degrees of freedom.
Shirts come in following sizes: XS, S, M, L, XL (3 degrees of freedom.
Or shirts sizes 4,6,8,10,12,14,16,18,20,22 (9 degrees of freedom) The increase in distinct catagories reduces the noise by more strictly defining the district catagories.0April 23, 2007 at 6:07 am #155102
Allthingsidiot OParticipant@AllthingsidiotO Include @AllthingsidiotO in your post and this person will
be notified via email.The F distribution has 2 degrees of freedom,d1 for the numerator,d2 for the denominator.For each combination of these degrees of freedom there is a different F distribution.As the degrees of freedom increase,the F distribution is less dispersed.In order to use the F table,first select the significance level (Alpha?) to be used,and then determine the appropriate combination of degrees of freedom.
good luck0April 23, 2007 at 2:14 pm #155126Try the following link with SME to see how many things SME can mean…
http://www.acronymfinder.com/0 
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