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# std

Standard deviation of probability distribution

## Syntax

``s = std(pd)``

## 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
`makedist`Create a probability distribution object using specified parameter values.
`fitdist`Fit 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.

## See Also

### Topics

Introduced in R2013a

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