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Evaluation Types GOMS and KLM

Evaluation Types GOMS and KLM. CS352. 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). Where we are in PRICPS :.

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Evaluation Types GOMS and KLM

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  1. Evaluation TypesGOMS 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 skilledusers, 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: • 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 opgranularitycombineslow-level ops.)

  17. KLM/GOMS example 1 (cont.) • Used to: • Understand cost of each. • (break downparticipants 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

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