Trying to Understand Three Sigma and Six Sigma
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- This topic has 12 replies, 9 voices, and was last updated 4 months, 2 weeks ago by
MBBinWI.
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- June 24, 2020 at 1:11 am #248556
[email protected]Participant@[email protected]Include @[email protected] in your post and this person will
be notified via email.if 99.7 % of the targets are within 3 sigma limits, then how exactly does 6 sigma explains itself? (how does iot affect the USL & LSL)
are we extending the tolerance levels? or confining the targets to be within the 6 sigma levels?
moreover is 6 standard deviations greater or lesser than 3 standard deviations in the normal distribution?
0June 26, 2020 at 2:09 am #248617
StrayerParticipant@StraydogInclude @Straydog in your post and this person will
be notified via email.I’m guessing that you’re conflating the +/- 3 sigma control limits in control charts with customer specification limits. They’re quite different. Control limits, calculated variation from the mean, tell us whether or not the process is under control. Whether or not variation is within specification limits is a different question.
- This reply was modified 6 months, 3 weeks ago by
Strayer.
1June 28, 2020 at 4:20 am #248661
Shamshul othmanParticipant@BaganInclude @Bagan in your post and this person will
be notified via email.I think u are confused abt spec limits and control limits. While they look the same but actually they are world apart. Spec limits are values provided by customer on their product specs. While control limits are guides on your input parameter range for production control purposes. While 99.7% looks good on low volume production, imagine if you are producing 30million pcs of semiconductor permonth, that 0.3% defects is equal to 900, 000pcs of defect every month.
0June 29, 2020 at 1:53 pm #248678
Mike CarnellParticipant@Mike-CarnellInclude @Mike-Carnell in your post and this person will
be notified via email.You need to take this a piece at a time, Start with you last question “moreover is 6 standard deviations greater or lesser than 3 standard deviations in the normal distribution?” If you cannot answer this or understand this then the discussion od control limits and spec limits will never make any sense to you.
0July 23, 2020 at 2:33 pm #249064
Chris SeiderParticipant@cseiderInclude @cseider in your post and this person will
be notified via email.@mike-carnell “what about 4.5 sigma”? :)
0July 23, 2020 at 2:46 pm #249065
Robert ButlerParticipant@rbutlerInclude @rbutler in your post and this person will
be notified via email.@cseider – well, welcome back…question – your elapsed time for your most recent group of responses is 62 minutes, 57 minutes, 14 minutes, 8 minutes, and 7 minutes….what happened between 57 and 14? Lunch break? :-)
Take Care
P.S. where I work the IT department is really on the ball as far as fighting Covid is concerned. This morning I logged in to work and shortly after I signed on I happened to sneeze. A split second later the computer started running an anti-virus program.
0July 23, 2020 at 3:03 pm #249066
Mike CarnellParticipant@Mike-CarnellInclude @Mike-Carnell in your post and this person will
be notified via email.@cseider Let’s see if I draw a line and mark 0 then mark off 1-10 at equal intervals on the line and then mark 3, 4.5 and 6 I might get a clue.
0July 26, 2020 at 11:24 am #249102
Fausto GalettoParticipant@fausto.galettoInclude @fausto.galetto in your post and this person will
be notified via email.Before asking questions one must study a bit ….
0July 27, 2020 at 11:39 pm #249124
Chris SeiderParticipant@cseiderInclude @cseider in your post and this person will
be notified via email.Sadly, I saw study materials from a course at a university MBA program state that 6 sigma is because of the +/- 3 sigma. Amazing how diluted the teachings are from the early 90s.
I wasn’t in the class but told the student that wasn’t six sigma meant.
0July 28, 2020 at 9:39 pm #249138
Gordon PaisleyParticipant@gpaisley1Include @gpaisley1 in your post and this person will
be notified via email.Seth,
I’ll take your question at face value since I’m new to the discussion.
The USL and LSL are given to you by your customer. These specifications determine the range of variability within which they will accept output variation.
The sigma levels describe how a process performs *with respect to* those limits. It describes how well the process meets the customer’s specifications.
99.7% sounds pretty good for a process, and depending on what you’re building, it may be decent, but in the industry I come from–the airline industry–I don’t think anyone would fly if 3 flights out of 1000 failed.
Gordon
0August 29, 2020 at 6:35 pm #249645
MBBinWIParticipant@MBBinWIInclude @MBBinWI in your post and this person will
be notified via email.@rbutler – Big Brother is always watching ;-}
0August 29, 2020 at 6:39 pm #249646
MBBinWIParticipant@MBBinWIInclude @MBBinWI in your post and this person will
be notified via email.@cseider – so, you’re telling me it aint? Oh, I get it, +3 and -3 must be Zero sigma ;-}
0August 29, 2020 at 6:41 pm #249647
MBBinWIParticipant@MBBinWIInclude @MBBinWI in your post and this person will
be notified via email.@Mike-Carnell – and don’t get me started on the whole “1.5 sigma shift” bullshizzle.
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