iSPC control limit alignment

[Former Member]

Hello,

I am using an iSPC chart and feeding in my own control limits. I have multiple (up to three) phases of control limit data, each with varying center lines, UCL and LCL's. I have two problems.

1) The control limits seem to be plotted before their corresponding point. By this I mean, the control limit's for a particular point are plotted in the space between that point and the previous point. I have included a link to a screen shot showing this. The point is circled in green and the control limit data for that point is also circled in green. What we would like is to have the point placed between the two tick parks, and the control limit lines centered between the ticks. Another way to look at it is the point would be centered above/below the corresponding control limit dash.

2) There appears to be no control limits on the chart for our first point, 12/31/2007. I have circled this in red.

Here is the link for the chart,

http://img59.imageshack.us/img59/3807/screenshots.jpg

Here is the link for the data,

http://img524.imageshack.us/img524/9678/screenshot2sa.jpg

Please ask any questions you may have.

Thank You for any help.

[salvatore_castro]

Nick,

Are you using the Auto-Calculate control limits since the posted dataset has NA set for the values which would be why they are not plotting? What is your subgroup size set to for the chart?

I know that in the next SP for v12.0, SPS 9, there is a newly added field around the centering a lines and control limit plotting. The field is a checkbox located in the General tab and is called "Center Control Limit Lines on Points" in order to resolve a similar issue.

Regards,

Sam

[Former Member]

Nick,

What version of MII are you using?

Kevin