Log-Laplace distribution
Probability distribution
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In probability theory and statistics, the log-Laplace distribution is the probability distribution of a random variable whose logarithm has a Laplace distribution. If X has a Laplace distribution with parameters μ and b, then Y = eX has a log-Laplace distribution. The distributional properties can be derived from the Laplace distribution.
| Log-Laplace distribution | |||
|---|---|---|---|
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Probability density function Probability density functions for Log-Laplace distributions with varying parameters and . | |||
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Cumulative distribution function Cumulative distribution functions for Log-Laplace distributions with varying parameters and . | |||
| Parameters |
(position), (scale) | ||
| Support | |||
| Mean | |||
| Median | |||
| Mode | |||
| Variance | |||
| Skewness | |||
| Excess kurtosis | |||
| Entropy | |||
Characterization
A random variable has a log-Laplace(μ, b) distribution if its probability density function is:[1]
The cumulative distribution function for Y when y > 0, is
Generalization
Versions of the log-Laplace distribution based on an asymmetric Laplace distribution also exist.[2] Depending on the parameters, including asymmetry, the log-Laplace may or may not have a finite mean and a finite variance.[2]
Properties
The mean or expected value of a log-Laplace distributed random variable X with a location parameter μ and a scale parameter b is given by
The variance of X is given by