Information Technology Reference
In-Depth Information
8.3 COMPARISON TO GOALS AND EXPERT
PERFORMANCE
Although the previous section focused on ways to summarize usability data
without reference to an external standard, in some cases you may have an exter-
nal standard that can be used for comparison. The two main flavors of an exter-
nal standard are predefined goals and expert, or optimum, performance.
8.3.1 Comparison to Goals
Perhaps the best way to assess the results of a usability test is to compare those
results to goals that were established before the test. These goals may be set at
the task level or an overall level. Goals can be set for any of the metrics we've dis-
cussed, including task completion, task time, errors, and self-reported measures.
Here are some examples of task-specific goals:
•
Atleast90%ofrepresentativeuserswillbeabletoreserveasuitablehotel
room successfully.
•
Opening a new account online should take no more 8 minutes on
average.
•
Atleast95%ofnewuserswillbeabletopurchasetheirchosenproduct
online within 5 minutes of selecting it.
Similarly, examples of overall goals could include the following:
•
Userswillbeabletocompleteatleast90%oftheirtaskssuccessfully.
•
Userswillbeabletocompletetheirtasksinlessthan3minuteseach,on
average.
UserswillgivetheapplicationanaverageSUSratingofatleast80%.
Typically, usability goals address task completion, time, accuracy, and/or sat-
isfaction. The key is that the goals must be measurable. You must be able to
determine whether the data in a given situation supports the attainment of the
goal. For example, consider the data in
Table 8.9
.
•
Table 8.9 Sample data from eight tasks showing target number of page visits and mean of actual
number of page visits.
Target # of Page Visits
Actual # of Page Visits
Task 1
5
7.9
Task 2
8
9.3
Task 3
3
7.3
Task 4
10
11.5
Task 5
4
7
Task 6
6
6.9
Task 7
9
9.8
Task 8
7
10.2
Table 8.9 Sample data from eight tasks showing target number of page visits and mean of actual number
of page visits.
Search WWH ::
Custom Search