Limits of Normal and Lognormal Distribution

For normal and lognormal distribution lower and upper limits are interpreted as follows:

•The standard deviation sigma is calculated to: sigma = (upper limit - lower limit) / 4, e.g. the range between upper and lower limit is 4·sigma.

•Because the normal distribution is open on both sides but negative values are not reasonable for most parameters these values are disregarded (in this case a new random value is calculated).

•There is no limit upwards, high values are highly improbable but possible.