The Lognormal Distribution

The lognormal distribution is a commonly used distribution for modelling asymmetric data.  It’s just the log of a Normal distribution right?  Well no, it’s actually the other way around.  You take the log of a lognormal distribution to arrive at a normal distribution.  Is it just me, but I always have a bit of a mental block about this, it always feels a bit back to front.

In this post I will explore the relationship between a lognormal distribution and a normal distribution.


Calculating dppm

In my last post I introduced the idea of using the JSL script editor as a simple command line calculator; and prior to that I discussed how process capability indices (Cp,Cpk) are a convenient shorthand notation but suffer from lack of transparency.  Today I will bring these two themes together by showing how I can use the JSL script editor to calculate defective parts per million (dppm) for a given set of capability indices Cp and Cpk.


Activity Status Class


The idea of object-orientation is not new to JSL, but user-created objects require a complex code structure that wraps data and functions into namespaces (for example, see the navigation wizard).

In version 14,  there is explicit support for classes which dramatically simplifies the process of creating reusable objects.  I thought I would introduce them by means of a real- example: a notification window that shows progress when stepping through a sequence of time-consuming steps.


Insights in the use of JMP and the scripting language JSL