var

Variance of probability distribution

Syntax

v = var(pd)

Description

example

v = var(pd) returns the variance v of the probability distribution pd.

Examples

collapse all

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 variance of the fitted distribution.

v = var(pd)
v = 76.0419

For a normal distribution, the variance is equal to the square of 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 variance of the distribution.

v = var(pd)
v = 5.3650

Create a triangular distribution object.

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

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

Compute the variance of the distribution.

v = var(pd)
v = 1.5556

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

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

Fit a kernel distribution object to the data.

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

    Kernel = normal
    Bandwidth = 3.61677
    Support = unbounded

Compute the variance of the fitted distribution.

v = var(pd)
v = 88.4893

Input Arguments

collapse all

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

collapse all

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

Introduced in R2013a