The Elsmar Cove Business Systems and Standards Discussion Forums How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)
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# How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

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Post Number #1
28th December 2011, 10:42 PM
 KCIPOH Total Posts: 181
How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

Hello Cove members,

I need help and would like someone to guide me on how to calculate UCL and LCL for the following attachment.

Can show me in detail for calculating the Mean, Std Dev (step by step)

Need help
Attached Files: 1. Scan for viruses before opening, 2. Please report any 'bad' files by Reporting this post, 3. Use at your Own Risk.
 UCL and LCL_a.xls (14.0 KB, 225 views)

Post Number #2
29th December 2011, 05:41 AM
 Stijloor Total Posts: 15,223
Re: How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

A Quick Bump!

Can someone help?

Thank you very much!

Stijloor.
Post Number #3
29th December 2011, 09:35 AM
 bobdoering Total Posts: 4,044
Re: How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

By looking at this data, I would have to ask what is this process? What kind of variable are you looking at? To calculate UCL and LCL, you have to pick the correct control chart. I see subgroups, but am not sure if they are adequate. What do the subgroups represent? Do you really want to calculate standard deviation long hand? Do you have a calculator or Excel?
Post Number #4
29th December 2011, 10:38 AM
 Darius Total Posts: 551
Re: How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

Sorry for deleting the previous response, I attached a file for powerpoint 2007 and saw that the file posted was on a previous version, so it can be seen, change it to 2003.
Attached Files: 1. Scan for viruses before opening, 2. Please report any 'bad' files by Reporting this post, 3. Use at your Own Risk.
 Average and Range Control Chart.ppt (192.5 KB, 352 views)
 Thank You to Darius for your informative Post and/or Attachment!
Post Number #5
29th December 2011, 10:45 AM
 bobdoering Total Posts: 4,044
Re: How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

Quote:
 In Reply to Parent Post by Darius I attached a file for powerpoint 2007 ...
Great post. I still bothers me to dump data into a chart without understanding if the chart - or the data - is adequate. It is just a bad way to look at SPC. Borders rubber stamp. That's why I posed the questions before posting the chart.
 Thanks to bobdoering for your informative Post and/or Attachment!
Post Number #6
29th December 2011, 12:50 PM
 AnaMariaVR2 Total Posts: 512
Re: How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

Darius...how do you obtain A2 & D4 from the tables?
Post Number #7
29th December 2011, 01:05 PM
 iamtroll Total Posts: 81
Re: How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

Quote:
 In Reply to Parent Post by AnaMariaVR2 Darius...how do you obtain A2 & D4 from the tables?
It depends on the sample size "n", see slide 4
 Thanks to iamtroll for your informative Post and/or Attachment!
Post Number #8
29th December 2011, 01:12 PM
 iamtroll Total Posts: 81
Re: How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

Quote:
 In Reply to Parent Post by bobdoering Great post. I still bothers me to dump data into a chart without understanding if the chart - or the data - is adequate. It is just a bad way to look at SPC. Borders rubber stamp. That's why I posed the questions before posting the chart.
I agree, but you have to start somewhere. If you have been tasked with charting a process, you often need to get on with it since your boss is not always willing to wait for you to gain the necessary knowledge to be an expert. I would hope that then that individual would recognize that their needs goes beyond the mechanics and must extend to the level of understanding. That understanding is not going to be found in this forum, as statistics need some fairly extensive study and training however we can help folks by giving folks a taste of what the statistics can tell them.

 The Elsmar Cove Business Systems and Standards Discussion Forums How to Calculate UCL (Upper Control Limits) and LCL (Lower Control Limits)

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