# Calculate Sample Size

Six Sigma – iSixSigma Forums Old Forums General Calculate Sample Size

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• #43094

DG
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I would like to know how to calculate the sample size to yield a positive lower control limit if a process is controlled using a p control chart with n=100, centre line = 0.08 and 3 sigma units UCL = 0.161, LCL = 0. Could you please also show me the workings – I have no idea.Thankyou to all who help.

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#136392

Ken Feldman
Participant

I would like to know how to calculate the sample size to yield a positive lower control limit if a process is controlled using a p control chart with n=100, centre line = 0.08 and 3 sigma units UCL = 0.161, LCL = 0. Could you please also show me the workings – I have no idea.The lower control limit for a p chart will either be zero or a positive value since you can’t have a negative proportion defective.  The 3 sigma units are based on the s.d. of a binomial distribution which will be different than a s.d. for a continuous distribution.  The formula for a p chart is as follows:UCLp= pbar + 3*sqrt[(pbar*(1-pbar))/n]LCLp = pbar – the same as aboveI still am not sure of your question but the above should provide enough info for you to figure it out.

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#186624

Fontanilla
Participant

There are some sample size calculators available here that may help:http://www.six-sigma-analyst.com/calculators.php

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