Statistics Toolbox™

capaplot - Process capability plot

Syntax

p = capaplot(data,specs)
[p,h] = capaplot(data,specs)

Description

p = capaplot(data,specs) estimates the mean of and variance for the observations in input vector data, and plots the pdf of the resulting T distribution. The observations in data are assumed to be normally distributed. The output, p, is the probability that a new observation from the estimated distribution will fall within the range specified by the two-element vector specs. The portion of the distribution between the lower and upper bounds specified in specs is shaded in the plot.

[p,h] = capaplot(data,specs) additionally returns handles to the plot elements in h.

Example

Simulate a sample from a process with a mean of 3 and a standard deviation of 0.005:

data = normrnd(3,0.005,100,1);

Compute capability indices if the process has an upper specification limit of 3.01 and a lower specification limit of 2.99:

S = capability(data,[2.99 3.01])
S = 
       mu: 3.0006
    sigma: 0.0047
        P: 0.9669
       Pl: 0.0116
       Pu: 0.0215
       Cp: 0.7156
      Cpl: 0.7567
      Cpu: 0.6744
      Cpk: 0.6744

Visualize the specification and process widths:

capaplot(data,[2.99 3.01]);
grid on

See Also

capability, histfit

capability

caseread