Need Help With Control Limits Question
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 This topic has 5 replies, 3 voices, and was last updated 3 years, 1 month ago by Chris Seider.

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August 21, 2017 at 10:43 am #55795
Amihai PantzParticipant@Ami.p Include @Ami.p in your post and this person will
be notified via email.Hiya all,
It seems easy one…Im trying to use the median Chart x+AR but I get wrong.
my n=8, x=12.62, A(8)=0.373….what is my mistake???A set of data from a process has 8 readings per sample and 50 samples. The mean of the
50 sample means is 12.62. The mean of the 50 ranges is 0.18.Find the control limits for a
median chart.
A. 12.52 and 12.72
B. 12.54 and 12.70
C. 0.02 and 0.33
D. none of the aboveThanks
0August 24, 2017 at 6:53 pm #201780
StrayerParticipant@Straydog Include @Straydog in your post and this person will
be notified via email.The reason no one answered this is probably that we resist doing your homework. What do you get for your answer? How did you decide on that answer? Tell us that and maybe someone well explain.
That said, this is the sort of exam question I despise. It may be an interesting intellectual exercise but it has little to do with actual practice. What you should know is under what circumstances you may prefer a control chart centered on the median over one centered on the mean.
0August 25, 2017 at 5:17 am #201781
Amihai PantzParticipant@Ami.p Include @Ami.p in your post and this person will
be notified via email.Hi,
I am trying to get ready for the six sigma black belt exam and found this question on one of the sites.
Homework…well…this is something I did long long time ago..Do you think those kind of questions are not in the IASSC exam?
I have no clue what questions I will have so I’m trying to answer all of them and all kinds of type.
General ones, which refers to wide knowledge of the terms and how to use the tols and ones that are more calculative, like calculate the LCL/UCL, MEDIUM, MEAN, COLORATION, MAIN EFFECT etc.
What do you think?I would really appreciate some help as I really(!!) can’t find a site that says “this is the sort of the question you will have” so I can focus..
Thanks,
Ami0August 25, 2017 at 8:53 am #201783
Chris SeiderParticipant@cseider Include @cseider in your post and this person will
be notified via email.https://www.qimacros.com/controlchartformulas/xmedianrchartformula/
One source for you to consider but did you check isixsigma.com ?
0August 27, 2017 at 5:42 am #201786
Amihai PantzParticipant@Ami.p Include @Ami.p in your post and this person will
be notified via email.Hi,
Thanks.
Yes I did looked at isixsigma.com but didn’t fined an exam.
Also the formula you gave me doesn’t gives the right result…that is what I am wondering about.0August 28, 2017 at 7:38 am #201791
Chris SeiderParticipant@cseider Include @cseider in your post and this person will
be notified via email.I wonder where the given A2 is a typo…if it’s .473 you get one of the answers. https://www.qualitydigest.com/dec98/html/spctool.html shows A2 would be in vicinity of 0.473
I also find it weird they worded it “mean of the means” instead “mean of the medians”. It looks like a poorly put together question that might even be testing the use of significant digits since A and B are so close to each other and I calculate “quickly” somewhere in between the two.
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