std

Class: prob.ToolboxFittableParametricDistribution
Package: prob

Standard deviation of probability distribution object

Syntax

s = std(pd)

Description

s = std(pd) returns the standard deviation s of the probability distribution pd.

Input Arguments

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pd — Probability distributionprobability distribution object

Probability distribution, specified as a probability distribution object. Create a probability distribution object with specified parameter values using makedist. Alternatively, create a probability distribution object by fitting it to data using fitdist or the Distribution Fitting app.

Output Arguments

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s — Standard deviationnonnegative scalar value

Standard deviation of the probability distribution, returned as a nonnegative scalar value.

Examples

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Standard Deviation of a Fitted Distribution

Load the sample data. Create a vector containing the first column of students' exam grade data.

load examgrades;
x = grades(:,1);

Fit a normal distribution object to the data.

pd = fitdist(x,'Normal')
pd = 

  NormalDistribution

  Normal distribution
       mu = 75.0083   [73.4321, 76.5846]
    sigma =  8.7202   [7.7391, 9.98843]

Compute the standard deviation of the fitted distribution.

s = std(pd)
s =

   8.7202

For a normal distribution, the standard deviation is equal to the parameter sigma.

Standard Deviation of a Skewed Distribution

Create a Weibull probability distribution object

pd = makedist('Weibull','a',5,'b',2)
pd = 

  WeibullDistribution

  Weibull distribution
    A = 5
    B = 2

Compute the standard deviation of the distribution.

s = std(pd)
s =
    2.3163

See Also

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