Statistics Toolbox

capaplot

Process capability plot

Syntax

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

Description

p = capaplot(data,specs) estimates the mean and variance of 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

Imagine a machined part with specifications requiring a dimension to be within 3 thousandths of an inch of nominal. Suppose that the machining process cuts too thick by one thousandth of an inch on average and also has a standard deviation of one thousandth of an inch.

• data = normrnd(1,1,30,1);
  p = capaplot(data,[-3 3])
  p =
      0.9784
  

The probability of a new observation being within specs is 97.84%.

See Also
capable, histfit

capable

caseread