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P-Chart VSS does not use VSS Size

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[quote][i]Originally posted by Bill Rokos[/i]
[br]Hello,

I am currently using the SPC Control Chart set to PERCENT_DEFECTIVE_PARTS_CHART_VSS.  When my chart is complete it seems to be taking the first Sample Sub Group Size and using it to determine Defective %.

1.  I load the chart type by calling:  Chart.SPCChartType = SPCControlChartData.PERCENT_DEFECTIVE_PARTS_CHART_VSS;

2.  I then go through my categories and build an array of defective count for each category.  At the last element I add my total defective count.

3.  After setting Table header info and control limits.

4.  I call Chart.ChartData.SampleSubgroupSize_VSS = sampleSubGroup.TotalSampleCount; to set the number of samples per sample sub group.

5.  I call  chart.ChartData.AddNewSampleRecord(index, samplesArrayFromAbove, UniqueStringOfSampleSubGroupAsNote);

6.  to set the scale I call chart.AutoScalePrimaryChartYRange();

7.  Then to use current data I call chart.RebuildChartUsingCurrentData();

I am not sure what I am doing wrong.  If you have any advice please let me know.  Also if you need additional information please let me know.

Defects	14	17	5	11	10	7	5	21	13	19
Sample Count	74	60	62	54	67	70	51	71	62	69
Expected Def%	0.189189189	0.283333333	0.080645161	0.203703704	0.149253731	0.1	0.098039216	0.295774648	0.209677419	0.275362319
Actual Def%	0.189189189	0.22972973	0.067567568	0.148648649	0.135135135	0.094594595	0.067567568	0.283783784	0.175675676	0.256756757

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T O P I C R E V I E W
Bill Rokos	Posted - 20 Mar 2014 : 21:28:01 Hello, I am currently using the SPC Control Chart set to PERCENT_DEFECTIVE_PARTS_CHART_VSS. When my chart is complete it seems to be taking the first Sample Sub Group Size and using it to determine Defective %. 1. I load the chart type by calling: Chart.SPCChartType = SPCControlChartData.PERCENT_DEFECTIVE_PARTS_CHART_VSS; 2. I then go through my categories and build an array of defective count for each category. At the last element I add my total defective count. 3. After setting Table header info and control limits. 4. I call Chart.ChartData.SampleSubgroupSize_VSS = sampleSubGroup.TotalSampleCount; to set the number of samples per sample sub group. 5. I call chart.ChartData.AddNewSampleRecord(index, samplesArrayFromAbove, UniqueStringOfSampleSubGroupAsNote); 6. to set the scale I call chart.AutoScalePrimaryChartYRange(); 7. Then to use current data I call chart.RebuildChartUsingCurrentData(); I am not sure what I am doing wrong. If you have any advice please let me know. Also if you need additional information please let me know. Defects 14 17 5 11 10 7 5 21 13 19 Sample Count 74 60 62 54 67 70 51 71 62 69 Expected Def% 0.189189189 0.283333333 0.080645161 0.203703704 0.149253731 0.1 0.098039216 0.295774648 0.209677419 0.275362319 Actual Def% 0.189189189 0.22972973 0.067567568 0.148648649 0.135135135 0.094594595 0.067567568 0.283783784 0.175675676 0.256756757
3 L A T E S T R E P L I E S (Newest First)
quinncurtis	Posted - 24 Mar 2014 : 20:05:43 There does seem to be something wrong with that version of AddNewSampleRecord. We will have to investigate further and find what the problem is.
Bill Rokos	Posted - 24 Mar 2014 : 17:49:07 Hello, So I did a lot of testing on this. I think I figured out what is causing my problem. So to test I used your C# sample called VariableSampleSizeControlCharts. In the SimulateData() function of the PercentDefectivePartsControlChart.cs I was able to change the call slightly and reproduce the error. In the sample code the VSS value works fine: this.ChartData.AddNewSampleRecord( timestamp, samples); If I change the call to: this.ChartData.AddNewSampleRecord(i, timestamp, samples, "Note"); The value in this.ChartData.SampleSubgroupSize_VSS = numsamplespersubgroup - (int)(25 * ChartSupport.GetRandomDouble()); seems to be ignored. Can you help me determine if this is as designed? Best Regards
quinncurtis	Posted - 20 Mar 2014 : 23:57:13 Using your data, we reproduced the results you say are correct. Can you send us a zip file of a complete program which reproduces the results you say you are getting.

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