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bscorb
USA
3 Posts |
 Posted - 02 Dec 2014 : 15:43:24
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We're collecting data in subgroups of size 5 yet seeing an LCL calculated for the R chart. It appears that a d3 constant of around -0.114 is being used. Shouldn't the LCL just be 0 in this case?
Brian |
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quinncurtis
1586 Posts |
Posted - 02 Dec 2014 : 23:39:19
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| Sorry, but you do not seem to be specifying enough information for us to comment. Our own examples (TimeVariableControlCharts.XBarRChart, BatchVariableControlCharts.BatchXBarRChart) produce as LCL of 0 using a sample subgroup size of 5, because the d3 value is 0 for that sample size. Please describe exactly what type of chart you are creating and show a picture of it, with the sample data values. |
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bscorb
USA
3 Posts |
Posted - 03 Dec 2014 : 14:40:11
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How do I post a picture on this forum?
I have an image saved of the R chart where the LCL shows as -0.093. The sample subgroup size is 5. I'm just confused why the d3 value isn't 0 for this graph and data. Instead, it calculates out to be around -0.114. This has occurred on several R charts. |
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quinncurtis
1586 Posts |
Posted - 03 Dec 2014 : 14:45:44
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Post an image using the Insert Image option (fourth icon from right on format bar). If you don't have a public URL to post the image on, you can use a free image posting service such as ImageShack, http://www.imageshack.us/.
In any reply, please state exactly which of our SPC Charts you are using.
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bscorb
USA
3 Posts |
Posted - 03 Dec 2014 : 15:44:45
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| Surely there's an easier way than signing up for imageshack. I don't have a public URL to post to. Can you please email me via my profile so I can forward you the image as an attachment? I can't email you that way because I haven't posted enough to the forum. |
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quinncurtis
1586 Posts |
Posted - 03 Dec 2014 : 15:53:20
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As a test, I signed up with ImageShack, and uploaded the image above, and it took only 5 minutes.
If you want, you can send your image to support@quinn-curtis.com . Or you can send us a complete project in a zip file that demonstrates the problem. Since we don't see your name in our order database, please identify whether or not you are a licensed user of the software, and if so, when it was purchased. If we can't see what is wrong based on your picture, we are going to ask you for an example project anyway.
Also, please identify exactly which SPC Chart you are using.
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R chart: LCL calculation
