Thank you for responding so quickly!
I see, so you're saying that it would be better to calculate the extreme value from the maximum/minimum itself, and not even use the standard deviation?
Its probably not standard, but the log-normal distribution I am using is from Sortino/Satchell p 57:
(
\tag{1}
\text{lognormal}(x) = \left\{ \begin{array}{l}
\frac{\alpha}{\tau-x}\exp(\beta(\ln(\tau-x) - \mu)) \; \mathrm{if}\, \tau > \overline{x} \\
\frac{\alpha}{x-\tau}\exp(\beta(\ln(x-\tau) - \mu))\; \mathrm{if}\, \tau < \overline{x}
\end{array}\right.
)
where,
(
\tag{1a}
\alpha=\frac{1}{\sigma\sqrt{2\pi}}
)
(
\tag{1b}
\beta=-\frac{1}{2\sigma^2}
)
If I understand correctly are you saying that the log-normal is not defined wherever the ((x-\tau)) or the ((\tau-x)) argument to ln in (1), above is less than zero?
