capaplot (Statistics Toolbox)

Process capability plot.

Syntax

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

Description

capaplot(data,specs) fits the observations in the vector data assuming a normal distribution with unknown mean and variance and plots the distribution of a new observation (T distribution.) The part of the distribution between the lower and upper bounds contained in the two element vector, specs, is shaded in the plot.

[p,h] = capaplot(data,specs) returns the probability of the new observation being within specification in p and 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%.