# computing the capability indices

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• #28059

Participant

I have tried several times,but I”m confusing,I’m asking for guidance of an expert to solve the following excercise:
A process was studied and the control limits set at 50.10+/-0.12.The sample size was 5(n=5).If the specifications are 50.00+/-0.20,compute the capability indices (Cp,Cpk,Cpl and Cpu.)Whatpercentage is the process capable?Not capable??show evidence…..Thanks in advance,Appreciate prompt response,regards

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#69489

gt
Participant

first:you need to know the mean(u) and  std deviation
short term indices, where std dev=R/d2
2nd: Cpk=min((u-lsl)/3stddev, (Usl-u)/3 stddev)
3rd Cp=(Usl-Lsl)/6 stddev
for long term we use the Pp and Ppk
instead of using std dev=R/d2, take the std dev of the sample
rgds

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#69492

Participant

thank you very much for advice,best regards

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#69524

kmb
Participant

I assume that you’re taking samples of size 5 from a stable process and trying to estimate the capability of your process.  You should check the assumptions, of course.  For more info you may wish to refer to the papers on capability analysis using MINITAB via http://www.minitab.com/company/virtualpressroom/Articles/index.htm including the confidence interval discussion paper.  Hope it helps.
-KMB

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#69554

Participant

The overall mean of  a set of sampllea is 24.The lower limit on the control chart is  10 and the upper limit is 42.The standard deviation  of the  sample data is 12.0 What is the process capability?
explain how you calculate it??
a.over 95%
b.between 90% and 95%
c.between 85% and 90%
d.between 80% and 85
e.under 80%

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#69557

Participant

1.WHAT ARE THE ADVANTAGES OF STUDYING  A SAMPLE INSTEAD OF A POPULATION??
2*sKETCH A BOXPLOT OF THE FOLLOWING STATISTICS:
SMAALEST=60,MEDIAN=100,LARGEST=115,1st quartile=80,3rd quartile=110
there are no outliers .comment on the shape of this distribution
3*Obtain  a newspaper with  a classified section and create a stem-and -leaf plot of the asking prices of 20 automobiles,selected at random

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#69559