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: 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!!

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

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.

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.

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.

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.

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, ...

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).

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

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

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.

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.

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).

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.)

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

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

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:

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

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

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

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