# XBar-R Chart Usage

Six Sigma – iSixSigma Forums Old Forums General XBar-R Chart Usage

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• #46274

Lee
Participant

I’m teach an introductory class on quality, in an industrial setting and teaching production workers, and am interested in understanding the degree of coverage I have for specific areas.
In the area of control charts I cover the use (not generation) of XBar-R charts.  That covers about 95+% of the applications in this plant.  Any estimates of how adequately that prepares the participants for work in other plants?  In other words, of all of the forms of control charts, do you have an estimate of how often xBar-R charts are used compared to the total of all options for plants in general?  I suspect that hard numbers do not exist, so your input is valued.

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#152714

Krishnam Raju PV
Participant

Hai
This is Krishnam Raju
When to use X-bar R charts

If any process 6 six sigma (standard deviation) = Tolerance     use X-bar R charts

Example

Shaft Outer diameter Spec. 15.00 to 20.00mm (Tolerance = 5.00 mm)

Collect 30 parts and measure Outer diameter and calculate standard deviation.

Assume that standard deviation found 0.80mm

Calculate six sigma (6 standard deviation) = 6×0.80 = 4.80mm
Therefore Six sigma (6 standard deviation) = less than tolerance (4.80 is less than 5.00mm) then use X bar R charts.

Krishnam Raju

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#152715

Darth
Participant

Your post was babbling nonsense.  As for the original post, xbar/r charts are the most common in high volume manfacturing processes since rational subgroups are pretty easy to identify.  Depending on what you are measuring and the frequency in which data occurs, you will find that I/MR charts are quite popular as well.  It might be useful for you to also cover the basic attribute control charts like the p-chart.  It is also quite popular and allows for the distinction between measuring continuous data and attribute/discrete data.

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#152722

D D
Participant

As Darth says, this is utter babbling nonsense.  Forget six sigma, go back to basics:
http://www.spcpress.com/pdf/Wh_Make_PBC_Work.pdf

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#152724

Mike Carnell
Participant

Darth,
I take about a month off (from the Forum) and come back to find the same silver tongued devil posting. Glad to see you are still spreading wisdom.
Regards

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#152734

Lee
Participant

What I was looking for was something of the below format (but have not yet seen it):
IMHO, XBar-R charts : 80% of the time, Attribute charts: 15% of the time, ImR Charts 5% of the time.
So, in practical across the industries in the US/World, what is your humble estimates of the percentages?

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