std

Standard deviation of probability distribution

Description

example

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

Examples

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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.

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

Create a triangular distribution object.

pd = makedist('Triangular','a',-3,'b',1,'c',3)
pd = 
  TriangularDistribution

A = -3, B = 1, C = 3

Compute the standard deviation of the distribution.

s = std(pd)
s = 1.2472

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

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

Create a probability distribution object by fitting a kernel distribution to the data.

pd = fitdist(x,'Kernel')
pd = 
  KernelDistribution

    Kernel = normal
    Bandwidth = 3.61677
    Support = unbounded

Compute the standard deviation of the fitted distribution.

s = std(pd)
s = 9.4069

Input Arguments

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Probability distribution, specified as a probability distribution object created using one of the following.

Function or AppDescription
makedistCreate a probability distribution object using specified parameter values.
fitdistFit a probability distribution object to sample data.
Distribution FitterFit a probability distribution to sample data using the interactive Distribution Fitter app and export the fitted object to the workspace.

Output Arguments

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

Extended Capabilities

Introduced in R2013a