This document provides an introduction to GOMS (Goals, Operators, Methods, and Selection rules), a usability analysis technique for quantitatively comparing the efficiency of different interface designs. It explains that GOMS involves defining a task, breaking it down into basic gestures like keystrokes and mouse clicks, applying mental operators, and adding up the time estimates for each step. An example compares the time taken to enter a date of birth on Facebook, Yahoo, and a single text field, finding the single field takes around half the time of the other options. The document encourages using GOMS alongside other qualitative usability tools and provides resources for learning more about the technique.
3. GOMS
It is a simple technique for quantitatively
comparing the efficiency of designs
BTW… when I say GOMS I mean
GOMS keystroke level Model
(KLM or KLM-GOMS)
Use it in conjunction with your
qualitative tools
8. When to use GOMS
There are 3 reasons you might want to use
GOMS analysis:
1. Speed matters
2. You need to convince stakeholders
3. You want to become a better designer
9. The premise
The time taken to perform a task is the sum of
the time it takes to perform the elementary
gestures that make up that task
10. The steps
1. Define the task
2. Break it down into its gestures
3. Apply mental operators
4. Add up the numbers
11. 1. Define the task
KLM models the interaction of an experienced
user doing a defined task.
12. 2. Break it down into its gestures
KLM has a basic set of gestures; each with a
typical time assigned to it - which is sufficient
for comparative analyses.
13. 2. Break it down into its gestures
Keying (K)
= 0.2 sec
14. 2. Break it down into its gestures
Pointing (P)
= 1.1 sec
15. 2. Break it down into its gestures
Homing (H)
= 0.4 sec
16. 2. Break it down into its gestures
Mentally preparing (M)
= 1.35 sec
17. 2. Break it down into its gestures
Responding (R)
= n sec
18. 3. Apply mental operators
The hardest part of KLM. But it all comes down
to chunking.
Gestures
Chunk Chunk Chunk
M + Chunk M + Chunk M + Chunk
19. 3. Apply mental operators
M + HPK
Helen of Troy: M + KKKKKKKKKKKKKKK
356.34: M + KKKKKK
KLM: M+ K M+ K M+ K
20. 4. Add up the numbers
HMPK
0.4 + 1.35 + 1.1 + 0.2
= 3.05 sec
21. Example: Date of birth
What's your pet way of collecting date of birth?
Facebook:
Yahoo:
Single masked
input field: