Evaluation Types GOMS and KLM CS352

Quiz

Announcements Notice upcoming due dates (web page). Where we are in PRICPE: –Predispositions: Did this in Project Proposal. –RI: Research was studying users. Hopefully led to Insights. –CP: Concept and initial (very low-fi) Prototypes due Design Gallery #1. –Evaluate throughout, repeat iteratively!! 3

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 skilled 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, Think,...

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).

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: –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). –“Rx”: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”) actualcalc’d

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