Information Technology Reference
In-Depth Information
One issue that commonly arises during a usability evaluation is how or when
to end a task if the user is not successful. In essence, this is the “stopping rule”
for unsuccessful tasks. Here are some of the common approaches to ending an
unsuccessful task:
1.
Tell the users at the beginning of the session that they should continue
to work on each task until they either complete it or reach the point at
which, in the real world, they would give up or seek assistance (from
technical support, a colleague, etc.).
2.
Apply a “three strikes and you're out” rule. This means that the users
get three attempts (or whatever number you decide) to complete a task
before you stop them. The main difficulty with this approach is defin-
ing what is meant by an “attempt.” It could be three different strat-
egies, three wrong answers, or three different “detours” in finding
specific information. However you define it, there will be a consider-
able amount of discretion on behalf of the moderator or scorer.
3.
“Call” the task after a predefined amount of time has passed. Set a time
limit, such as 5 minutes. After the time has expired, move on to the next
task. In most cases, it is better not to tell the user that you are timing
them. By doing so, you create a more stressful, “test-like” environment.
Of course, you always have to be sensitive to the user's state in any usability
test and potentially end a task (or even the session) if you see that the user is
becoming particularly frustrated or agitated.
4.2 TIME ON TASK
Time on task (sometimes referred to as task completion time or simply task
time) is a good way to measure the efficiency of a product. In most situations,
the faster a user can complete a task, the better the experience. In fact, it would
be pretty unusual for a user to complain that a task took less time than expected.
But there are some exceptions to the assumption that faster is better. One could
be a game, where the user doesn't want to finish it too quickly. The main purpose
of most games is the experience itself rather than quick completion of a task.
Another exception may be e-learning. For example, if you're putting together
an online training course, slower may be better. Users may retain more if they
spend more time completing the tasks rather than rushing through the course.
TIME ON TASK VS WEB SESSION DURATION
Our assertion that faster task times are generally better seems at odds with the view from
web analytics that you want longer page view or session durations. From a web-analytics
perspective, longer page-view durations (the amount of time each user is viewing each
page) and longer session durations (the amount of time each user is spending on the
site) are generally considered good things. The argument is that they represent greater
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