Design of Human-Computer Interaction - Human Factors and Ergonomics - page 134

c. Will the user associate the correct action with the desired effect?
d. If the correct action is performed, will the user see that progress is being made?
• Record problems. Identify failure stories. The analyst should identify and document
all the problems in a failure story, the reason for failure, and the assumption about
the user's behavior. Consider and record design alternatives. Modify the interface
design to eliminate the problem.
GOALS, OPERATORS, METHODS, AND SELECTION (GOMS)
GOMS is a task analysis method. It uses a notation and syntax that is similar to
traditional programming languages (Card, Moran, and Newell, 1980). A GOMS model
consists of the following elements:
1. Goal —a specification of what a user wants to achieve, such as finding a word in a
manuscript that is being edited.
2. Operators —the actions that the analyzed software allows a user to take, such as
keyboard input, mouse input, or voice recognition input.
3. Method —methods that can be used to accomplish a goal. For example: to find a
specific word in a manuscript, such as NASA-TLX, one can either employ the method
of using the Find routine, which is listed under Edit in MS Word, or one can use the
method of simply scrolling down the text and searching for the word.
4. Selection —rules that a user follows in deciding which method to use in a particular
instance. For example, a user may utilize the following decision rules:
• If it is a long document, use the Find routine.
• If it is a short document, use the Scroll function, since it will be quicker.
GOMS is actually the wrong acronym. It should be GMSO. The user will first select a
goal, then consider what methods are available to accomplish the goal, then select a
suitable method, and finally use an operator (e.g., a keyboard) to expedite the selected
method.
To find the word in the document, we can program the two methods (see Table 7.6).
Method A takes five steps. Method B takes three steps if the word is on the first page. If
the word is on the second page it takes five steps. If it is on the third page it takes seven
steps, and so forth.
TABLE 7.6 Two Alternative Methods for
Finding a Document
Method A. Find a word using the find routine
Step 1. Accomplish goal: click on Edit
Step 2. Select Find
Step 3. Input word
Step 4. Click on Find Next
Step 5. Return with goal accomplished
Method B. Find a word by visually scanning pages
Step 1. Accomplish goal: search current page