Researching Usability

Author Archive

When carrying out usability studies on search interfaces, it’s often better to favour interview-based tasks over pre-defined ‘scavenger-hunt’ tasks. In this post I’ll explain why this is the case and why you may have to sacrifice capturing metrics in order to achieve this realism.

In 2006, Jared Spool of User Interface Engineering wrote an article entitled Interview-Based Tasks: Learning from Leonardo DiCaprio in it he explains that it often isn’t enough to create test tasks that ask participants to find a specific item on a website. He calls such a task a Scavenger-Hunt task. Instead he introduces the idea of interview-based tasks.

When testing the search interface for a library catalogue, a Scavenger Hunt task might read:

You are studying Russian Literature and your will be reading Leo Tolstoy soon. Find the English version of Tolstoy’s ‘War and Peace’ in the library catalogue.

I’ll refer to this as the Tolstoy Task in this post. Most of your participants (if they’re university students) should have no trouble understanding the task. But it probably won’t feel real to any of them. Most of them will simply type ‘war and peace’ into the search and see what happens.

Red routes

The Tolstoy Task is not useless, you’ll probably still witness things of interest. So it’s better than having no testing at all.

But it answers only one question – When users know the title of the book, author and how to spell them both correctly, how easy is it to find the English version of Leo Tolstoy’s War and Peace?

A very specific question like this can still be useful for many websites. For example a car insurance company could ask – When the user has all of his vehicle documents in front of him, how easy is it for them to get a quote from our website?

Answering this question would give them a pretty good idea of how well their website was working. This is because it’s probably the most important journey on the site. Most websites have what Dr David Travis calls Red Routes – the key journeys on a website. When you measure the usability of a website’s red routes you effectively measure the usability of the site.

However many search interfaces such as that for a university library catalogue, don’t have one or two specific tasks that are more important than any others. It’s possible to categorise tasks but difficult to introduce them into a usability test without sacrificing a lot of realism.

Interview-based tasks

The interview-based task is Spool’s answer to the shortfalls of the Scavenger Hunt task. This is where you create a task with the input of the participant and agree what successful completion of the task will mean before they begin.

When using search interfaces, people often develop search tactics based upon the results they are being shown. As a result they can change tactics several times. They can change their view of the problem based upon the feedback they are getting.

Whilst testing the Aquabrowser catalogue for the University of Edinburgh, participants helped me to create tasks that I’d never have been able to do so on my own. Had we not done this, I wouldn’t have been able to observe their true behaviour.

One participant used the search interface to decide her approach to an essay question. Together we created a task scenario where she was given an essay to write on National identity in the work of Robert Louis Stevenson.

She had decided that the architecture in Jekyll and Hyde whilst set in London, had reminded her more of Edinburgh. She searched for sources that referred to Edinburgh’s architecture in Scottish literature, opinion on architecture in Stevenson’s work and opinion on architecture in national identity.

The level of engagement she had in the task allowed me to observe behaviour that a pre-written task would never have been able to do.

It also made no assumptions about how she uses the interface. In the Tolstoy task, I’d be assuming that people arrive at the interface with a set amount of knowledge. In an interview-based task I can establish how much knowledge they would have about a specific task before they use the interface. I simply ask them.

Realism versus measurement

The downside to using such personalised tasks is that it’s very difficult to report useful measurements. When you pre-define tasks you know that each participant will perform the same task. So you can measure the performance of that task. By doing this you can ask “How usable is this interface?” and provide an answer.

With interview-based tasks this is often impossible because the tasks vary in subject and complexity. It’s often  then inappropriate to use them to provide an overall measure of usability.

Exposing issues

I believe that usability testing is more reliable as a method for exposing issues than it is at providing a measure of usability. This is why I favour using interview-based tasks in most cases.

It’s difficult to say how true to life the experience you’re watching is. If they were sitting at home attempting a task then there’d be nobody watching them and taking notes. Nobody would be asking them to think aloud and showing interest in what they were doing. So if they fail a task in a lab, can you be sure they’d fail it at home?

But for observing issues I feel it’s more reliable. If participants misunderstand something about the interface in a test, you can be fairly sure that someone at home will be making that same misunderstanding.

And it can never hurt to make something more obvious.

Advertisements

del.icio.us bookmarks

Twitter feed

Archive

Advertisements