### Calculation of Capability Based on Normal Distribution Parameters

If X1, X2, . . . Xn is the set of sample measurement values, normal distribution parameters are calculated using the following formulae:

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Mean:

`mu = (sum x_i)/n`

`sigma = sqrt (sum(x_i-mu)^2/(n-1))`

`sum_(i=1)^n i=(n(n+1))/2`

Sigma:

`Pp = ((USL * LSL))/(6sigma)`

`Ppu = ((USL - mu))/(3sigma)`

`Ppl = ((mu - LSL))/(3sigma)`

`Ppk = \M\i\n(Ppu,Ppl)`

[If no lower tolerance exists, then `Ppk=Ppu`]