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Formal vs. Informal Usability Tests

April 09, 2007

Wireframe What type of usability tests should you be conducting and why?

Formal Usability Testing

Also called "High Fidelity" usability testing.

Where it gets it's name: Design concepts are typically more finalized. Formal testing can take place in pre-release design, but not always. Websites in their current state (before a re-design) are considered Hi-Fi tests.

How common is it? Very common- even more common than informal usability testing. 

Advantages: Click-able prototypes are easier to follow (for stakeholders). Formal usability testing is often the test of choice for including developers, project managers, executives etc.

Drawbacks: A certain level of HTML "smoke and mirrors" design needs to be created (for web sites). More level of coding complexity is involved in testing software applications- in this case Informal testing is better.

Informal Usability Testing

Also called "Low Fidelity" usability testing or "paper prototype" testing.

Where it gets it's name: Design concepts are tested in draft "wireframe" or unpolished state. No coding or graphic design has occurred at this level. The focus is solely testing the "information architecture" or the "interaction design".

How common is it? Very common, contrary to what most marketers might think. Usability guru, Jakob Nielsen called this testing "Guerilla HCI" to refer to the fast and frequent use of this technique in corporate environments. However, most low-fi testing is usually done by usability engineers, with users behind closed doors or "in the trenches".

Advantages:  Yes! You can get design feedback early on. Feedback can be rapidly acquired in less than two weeks and inserted into the development lifecycle rapidly. A benefit for the quick turn Agile development cycles.

Drawbacks: You can't always test dynamic page level interactions. This will become more of a problem as "Web 2.0" interface design elements become more mainstream (such as fading and hovering elements).

Mixed Fidelity Usability Testing

Mixed-Fi? Mixed fidelity tests are more common for us at Experience Dynamics. We typically test with low-fi concepts that are "taped together" with HTML and some JavaScript. This gives us a rapid "cut and paste" site that can be iterated and refined on the fly. Informal HTML prototypes allow us to prototype and test quickly thereby keeping costs down, but still including stakeholders in our usability labs or remote testing sessions (more on Remote Usability Testing in a future post).

Conclusion: Usability testing can and should be done early on and throughout the product design lifecycle. It is very common for usability practitioners to test concepts that only exist on paper or as static PhotoShop files. Moreover, with basic HTML, a hybrid fidelity can be achieved bringing both the need for speed and user validation to a design.

Happy Usability Testing!
Frank Spillers, MS (Usability Consultant)

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