### Log Normal Distribution

The log normal distribution is often used when a set of measurements is badly skewed, but taking the logarithm of the measurements produces a distribution that is approximately normal. The log normal distribution has three parameters. The parameter a is the limiting value; no measurements will exist that are less than a. The parameter is the mean of the transformed (after logarithm) data. The parameter is the standard deviation of the transformed data. The probability density and distribution functions are given by: