HE-75, Usability and When to Prototype and Usability Test: Take 1

Prototyping and Testing will be a topical area where I shall have much to contribute.  Expect numerous articles to appear on this topic.

I had a discussion a few days ago with one of my colleagues who has worked as a user interface designer, but has little knowledge of human factors.  He was completely unaware of the concepts of "top-down" and "bottom-up" processes to user interface design.  I provide for you the essence of that discussion.

Top-Down Approach

The top-down approach begins with a design.  Most often the initial design is a best or educated guess based on some set of principles.  Could be aesthetics or "accepted" standards of good design, or something else.  The design is usability and/or acceptance tested in some manner.  (Anywhere from laboratory testing to field-collected data.)  In response to the data, the design reworked.  The process is continual.  Recent experience has suggested that the top-down approach has become predominant design methodology, particularly for the development of websites.

Top-down is a valid process, particularly for the deployment of new or unique products where the consequences of a failed design do not lead to serious consequences.  It can get a design into user hands more quickly.  The problem with a top-down approach (when practiced correctly) is that it relies on successive approximations to an ill-defined or unknown target.  To some degree it's similar to throwing darts blindfolded with some minimal correction information provided after each throw.  The thrower will eventually hit the bull's eyes, but it may take lots and lots of throws.

The top-down approach may have a side benefit in that it can lead to developing novel and innovative designs.  Although, it can have the opposite effect when designs are nothing more than "knock-offs" of the designs from others.  I have seen both coming out of the top-down approach.

Bottom-Up Approach

HE-75 teaches the use of a bottom-up approach where first one defines and researches the targeted user population.  Contextual Inquiry is also a bottom-up approach.  Since I have already discussed researching the targeted user population in depth, I'll not cover it here.  

With the bottom-up approach, the target is clear and understood.  And tailoring a design to the user population(s) should be a relatively straight forward process.  Furthermore, the bottom-up approach directly addresses the usefulness issue with hard data and as such, more likely to lead to the development of a system that is not only usable, but useful.

Useful vs. Usable

I'll address this topic more deeply in another article.  It suffices to say that usability and usefulness are distinctly different system qualities.  A system may be usable, that is, the user interface may require little training and be easy to use, but the system or its capabilities are not useful.  Or, and this is what often happens particularly with top-down approaches, much of what the system provides is not useful or extraneous.

Personal Preference

I am a believer in the bottom-up approach.  It leads to the development of systems that are both usable and useful sooner than the top-down approach.  It is the only approach that I would trust when designing systems where user error is of particular concern.  The top-down approach has its place and I have used it myself, and will continue to use it.  But, in the end, I believe the bottom-up approach is superior, particularly in the medical field.