The 2 Parameter Lognormal Distribution 7 Formulas

The 2 Parameter Lognormal Distribution 7 Formulas

This is part of a short series on the common life data distributions.

The Lognormal distribution is a versatile and continuous distribution. It is similar to the Weibull in flexibility with just slightly fatter tails in most circumstances. It is commonly used to describe time to repair behavior. This short article focuses on 7 formulas of the Lognormal Distribution.

If you want to know more about fitting a set of data to a distribution, well that is in another article.

It has the essential formulas that you may find useful when answering specific questions. Knowing a distribution’s set of parameters does provide, along with the right formulas, a quick means to answer a wide range of reliability related questions.

Parameters

The scale parameter, μ-sub N is the mean of the normally distributed natural logarithm of the data, ln(x). Unlike the normal distribution this parameter is only the scale and not the location. The scale parameter ranges from -∞ < μ-sub N < ∞ and if found from the data with:

The shape parameter, σ^2-sub N is the standard deviation of the normally distributed ln(x). Unlike the normal distribution this…