# Log Normal (Cobb-Douglass) Distribution¶

Has one shape parameter $$\sigma$$ >0. (Notice that the “Regress “$$A=\log S$$ where $$S$$ is the scale parameter and $$A$$ is the mean of the underlying normal distribution). The standard form is $$x>0$$

\begin{eqnarray*} f\left(x;\sigma\right) & = & \frac{1}{\sigma x\sqrt{2\pi}}\exp\left[-\frac{1}{2}\left(\frac{\log x}{\sigma}\right)^{2}\right]\\ F\left(x;\sigma\right) & = & \Phi\left(\frac{\log x}{\sigma}\right)\\ G\left(q;\sigma\right) & = & \exp\left\{ \sigma\Phi^{-1}\left(q\right)\right\} \end{eqnarray*}
\begin{eqnarray*} \mu & = & \exp\left(\sigma^{2}/2\right)\\ \mu_{2} & = & \exp\left(\sigma^{2}\right)\left[\exp\left(\sigma^{2}\right)-1\right]\\ \gamma_{1} & = & \sqrt{p-1}\left(2+p\right)\\ \gamma_{2} & = & p^{4}+2p^{3}+3p^{2}-6\quad\quad p=e^{\sigma^{2}}\end{eqnarray*}

Notice that using JKB notation we have $$\theta=L,$$ $$\zeta=\log S$$ and we have given the so-called antilognormal form of the distribution. This is more consistent with the location, scale parameter description of general probability distributions.

$h\left[X\right]=\frac{1}{2}\left[1+\log\left(2\pi\right)+2\log\left(\sigma\right)\right].$

Also, note that if $$X$$ is a log-normally distributed random-variable with $$L=0$$ and $$S$$ and shape parameter $$\sigma.$$ Then, $$\log X$$ is normally distributed with variance $$\sigma^{2}$$ and mean $$\log S.$$

Implementation: scipy.stats.lognorm

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