Articles

Stability studies are used to understand and model the degradation of key product characteristics over time.  They are often used to determine the product’s shelf life (the length of time a product may be stored without becoming unfit for use or consumption).

Shelf-Life studies should identify the potential “failure modes” and how they will assessed/ measured.  Examples of characteristics that are measured often include appearance attributes, texture, taste, microbial counts, and product effectiveness/performance.

(and Why Design of Experiments is so Superior)

In my 30-year career as an Industrial Statistics consultant, I have frequently been told by clients that they have performed Design of Experiments (DOEs), to try and resolve design or manufacturing issues.  What has become clear is that many engineers and scientists apply a rather liberal definition to DOE and include any type of experimentation in what they deem to be “DOE”.  

The reality is, simplistic or haphazard “experiments” rarely are effective in solving problems, especially complex ones.  Statistically based DOE provides several advantages over more simplistic approaches such “trial and error” or “one-factor-at-a-time” experimentation.  These advantages include:

• The use of statistical methodology (hypothesis testing) to determine which factors have a statistically significant effect on the response(s)
• Balanced experimental designs to allow stronger conclusions with respect to cause-and-effect relationships (as opposed to just finding correlations)
• The ability to understand and estimate interactions between factors
• The development of predictive models that are used to find optimal solutions for one or more responses

Each of these advantages are discussed in a bit more detail below.