CMSC 434 - Spring 2006
Prof Guimbretiere

Introduction to Human-Computer Interaction
Home Contact Syllabus Schedule HW & Project Links

Homework #5:
(Due 03/28/06)

1) (60 points) GOMS model

In this problem you will be providing a GOMS style analysis of the following task:

After finishing typing a document using MS Word, a user is trying to find and replace a misspelled word.

  1. (10 points) Describe the goals and sub-goals used

  2. (10 points) Describe the operators used

  3. (20 points) For each goals and sub-goals describe which method(s) could be used. (If there is more than 3 possible methods for a given goal (or sub-goal) list at least 3 of the most commonly used methods),

  4. (10 points) Describe the most probable selection rules for each goal (or sub-goal)

  5. (10 points) Present a synthesis of your work using the standard GOMS style shown in class.

While answering questions above, please keep in mind the following facts about this task:

  • The document can be as small as a single sentence, or as big as a book,

  • The search and replace may apply to a any part of the document (including the whole document),

  • The misspelling of a word may be context dependent, e.g. if the word "owe" is misspelled as "own". (You may assume that during the search process, new matches are always presented with enough context on screen for the user to make a decision without navigating the document.)

  • You may assume that the search is only concerned with characters (not character attributes such as style and the like) and that the search style (such as Match case, Whole words only... and the like) has been set once and for all before starting the search.

Please note: In a way, one may think about this analysis as writing a program to perform a task using basic operators. Accordingly grading will take into account the style of the decomposition and the comments/explanations provided.

2) (40 points) KLM model

Below is a simple interface to convert temperature between Fahrenheit and Celsius. To perform a conversion, the user selects the type of conversion with a mouse, then type a value to be converted on the left side and read the conversion result on the right. The conversion starts when the user press the “OK” button.

Assume the above is the initial state of the interface. Using the KLM model, predict the time that a user will take to:

  1. (20 points) convert 24.5°F to Celcius,

  2. (20 points) convert -78.4°C to Fahrenheit.

In both case, you can assume that the user is starting the interaction with her hands on the keyboard, and need to click on the left text field to set the focus. Be careful to explain your derivation (including which rule you are using) for partial credit. You can ignore the system response time and assume the following values for the KLM parameters: tK = .15s, tP = 1s, tH = .3s, tD = (9*n + .16*l)s, tM = 1.2s.