Syntax

Description

S = capability(data,specs)estimates capability indices for measurements indatagiven the specifications inspecs.datacan be either a vector or a matrix of measurements. Ifdatais a matrix, indices are computed for the columns.specscan be either a two-element vector of the form[L,U]containing lower and upper specification limits, or (ifdatais a matrix) a two-row matrix with the same number of columns asdata. If there is no lower bound, use-Infas the first element ofspecs. If there is no upper bound, useInfas the second element ofspecs.

The outputSis a structure with the following fields:

• mu— Sample mean

• sigma— Sample standard deviation

• P— Estimated probability of being within limits

• Pl— Estimated probability of being belowL

• Pu— Estimated probability of being aboveU

• Cp—(U-L)/(6*sigma)

• Cpl—(mu-L)./(3.*sigma)

• Cpu—(U-mu)./(3.*sigma)

• Cpk—min(Cpl,Cpu)

Indices are computed under the assumption that data values are independent samples from a normal population with constant mean and variance.

Indices divide a "specification width" (between specification limits) by a "process width" (between control limits). Higher ratios indicate a process with fewer measurements outside of specification.

References

See Also

capaplot|histfit