1. Evaluation Types GOMS and KLM
CS352

2. Announcements Mid-term Tue of Week 5 Project presentations
Your users (before mid-term)
Next milestone of you project will be out later today or tomorrow (Prototypes)
Reading
12.3 (evaluation methods), 15.4 (GOMS)

3. Where we are in PRICPS: Predispositions: Did this in Project Proposal.
RI: Research was studying users. Hopefully led to Insights.
CP: Concept and initial (very low-fi) Prototypes due some time next week
 Evaluate throughout, repeat iteratively!!

4. Evaluation Analytical – based on your head Empirical – based on data
Formative
inFORMs design
what is (still) needed?
Summative
did it work?

5. Analytical methods
You follow established guidelines/procedures/models to decide (in your head) how good your design is.
Examples:
GOMS/KLM – for skilled users, no errors.
evaluating efficiency of regular use.
Heuristic Evaluation
Cognitive Walkthrough – for first-time users.
evaluating ease of learning.

6. GOMS (and KLM) GOMS: a family of models. Predict user performance.
Useful for predicting actual time a user will take in UI.
Useful for comparing different UIs.

7. GOMS Constructs Goal, Operators, Methods, Selection rules
Goal: “what”.
Method: “how” steps (learned).
Operators: Cognitive processes + physical actions to DO it.
Selection rules: rules saying which method to select.

8. GOMS example: Delete a word
Goal: delete a word in a sentence.
Method #1: use the menu
Recall that the word has to be highlighted.
Recall that the command is “cut”.
Recall that “cut” is in the Edit Menu.
Accomplish goal of selecting and executing “cut”.
Return: goal accomplished.

9. GOMS example (cont.) Method #2: use the delete key
Recall where to position cursor in relation to word to be deleted.
Recall which key is delete key.
Press “delete” key to delete each letter.
Return: goal accomplished.
Operators used in these methods
Click mouse, Drag cursor over text, Select menu, Move cursor, Press KB key, Recall, ...

10. GOMS example (cont.) Selection rules:
Use mouse/menu method (#1) if there’s a lot of text to delete.
Else use “delete” key (method #2).

11. Applications of GOMS Various application and fields
Telephone operator workstation using CPM-GOMS
CAD system for ergonomic design using NGOMSL
Intelligent tutoring system using NGOMSL
Mouse driven text editor using KLM
Bank deposit reconciliation system using KLM
Space operations database system using KLM

12. Telephone operator workstation using CPM-GOMS
The task: a telephone company operator responding to customer requests for assistance.

13. Limitations of GOMS [Card et al. (1980) ]
applied to skilled users, not to beginners or intermediates.
doesn't account for either learning of the system or its recall after a period of disuse.
doesn't account for errors.
does not address the amount and kind of fatigue
individual differences among users is not accounted for in the model.

14. KLM (a low-level variant of GOMS)
Keystroke Level Model.
Simple, but accurate. Widely used.
Scope:
skilled users
doing a task error-free.
using a specific method in a UI.
CogTool has this built-in.

15. KLM Operators User Operators: System Operator:
K (keystroke), P (point), H (homing), D (drawing), M (mental: think).
Times for each are provided to you
based on extensive research/empirical data.
System Operator:
R (respond).

16. KLM/GOMS example 1: Open a file
27 ways to open a file in Windows!
Methods as states + transitions.
(High op granularity combines low-level ops.)

17. KLM/GOMS example 1 (cont.)
Used to:
Understand cost of each.
(break down participants actual costs).
“RL”:recent lists.
“WS/WX”:search.
And to...

18. KLM/GOMS example 1 (cont.)
Use the breakdowns to compare costs to new UI alternative (new feature “FP”)
actual
calc’d

19. Hick’s Law GOMS’s “S” stands for “Selection”
Hick’s Law predicts the time to make a choice between multiple choices, n is the # of choices:

20. Fitts’ Law
Predicts that the time required to rapidly move to a target area is a function of the distance to and the size of the target

21. In practice… GOMS not used often
Fitts’ law often used for determining best case for new kinds of input methods

22. CogTool Example CogTool examples.
Calculating the cost of the task in this UI.
Comparing the cost if do the task with different widgets.
Where are these cost differences coming from?
under the hood to ACT/R

23. What’s coming up next: Heuristic Evaluation Cognitive Walkthroughs
Empirical Studies