I've just finished reading "S60 Smartphone Quality Assurance" book, written by Saila Laitinen. This led me to some thoughts about  quality of final products. One part of the process of creating the product is testing. 

Probably many of you are familiar with words like 'constructive / destructive testing' or 'white-box / black-box testing'. But it may be challenging task to decide which part of the code to inspect the most. One way is to use Estimated Degree of Functional Usage (EDFU). As Saila wrote in her book "EDFU is a numeric value that provides a simple estimate of how often the end-user uses a certain piece of functionality. To determine this one needs to understand consumers' behaviour very well. If the value is one, it is estimated that the end user uses this particular piece of functionality every time he or she uses the product. If the value is close to zero (e.g. 0,01), it is very unlikely that na average user ever uses such functionality." A good question to ask is how to define an average user. Normally, we target our applications to certain customer groups. When we find people that match our profile we can ask them to use our prototype application and watch how this potential customer group uses it. "The higher the EDFU, the more important it is for that part or function to work properly. However, even such features that have a value 1 for EDFU are not automatically equally important from testing viewport. Those features whose implementation results in architecturally complex solutions should receive the most testing attention." Of course, this idea can be used in the process of developing not only mobile applications.

What do you think about EDFU? Would it be useful in your cases?