8 Ways to Sunday

Garrett Dimon has made some good comments on software documentation and usability, but the maxim he sets out is a little too fuzzy: “The length of your instructional text is almost always inversely proportionate to the usability of your product.” To truly quantify the usability of a piece of software, you have to consider the opposite scenario — a generally good interface with poor documentation.

Using Garrett’s idea as a starting point, and applying fifteen minutes of my own deep thought and extensive research, I have arrived at the following formula to unfailingly and scientifically measure the usability and/or documentation adequacy of any piece of software. This should work for web applications, desktop applications, and web sites:

In this equation u is the usability ratio of a program, d is the length of the documentation in words, and n is the number of features implemented. Basic UI conventions, like toolbars with clickable buttons, should not be counted toward n.

Software teams can judge the results of the calculation according to the following criteria:

• 7.6 and higher: The application is too complicated or confusing for the number of things it’s trying to do. Simplify the user interface for the application’s features and remove features that are rarely used. Create a user interface bible that dictates standards, conventions, and metaphors for the application’s interface. Make UI designers and programmers stick to the bible under penalty of death. If you have the budget, conduct a usability study.
• 5.7 to 7.5: The application may be suffering from feature creep or a poorly implemented user interface. The problem is not yet so far out of hand that huge efforts are needed to fix it. Applications with scores in this range may be facing growing pains associated with increased popularity and an expanding user base. Alternatively, the documentation may be bloated and over-written.
• 3 to 5.6: Congratulations, you have a good documentation-to-feature ratio. Chances are pretty good that your user interface doesn’t require too much head-scratching to figure out, and that users who do have problems will be able to solve them by reading the documentation.
• 1 to 2.9: Either the documentation is inadequate or the user interface is too complicated.
• 0-0.9: Little or no documentation provided. Bad developers! No cookie!

The basic idea here is that each major feature of a software application probably needs at least 300 words of documentation, on average. Any less, and your documentation may be inadequate for your users’ needs. Conversely, if you really need more than that your user interface could probably use some work.

Programmers and designers struggling with usability problems for web sites or web applications might benefit from reading some of the better books on the subject. For usability issues in general, the seminal work on the subject is Donald Norman’s The Design of Everyday Things. It’s technological references are a little dated now, but the core principles still hold true.

(Props: Garrett Dimon)