GOMS analysis

On the back of the envelope

GOMS

Is not a venereal disease...

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

+

You'll need the following tools

+ +

A quick story...

Deutsche Bank Trading Floor

London 2011

Numbers are compelling

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

When to use GOMS

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

The steps

1. Define the task

2. Break it down into its gestures

3. Apply mental operators

4. Add up the numbers

1. Define the task

KLM models the interaction of an experienced

user doing a defined task.

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.

2. Break it down into its gestures

Keying (K)

= 0.2 sec

2. Break it down into its gestures

Pointing (P)

= 1.1 sec

2. Break it down into its gestures

Homing (H)

= 0.4 sec

2. Break it down into its gestures

Mentally preparing (M)

= 1.35 sec

2. Break it down into its gestures

Responding (R)

= n sec

3. Apply mental operators

The hardest part of KLM. But it all comes down

to chunking.

M +

Chunk Chunk Chunk

Chunk M + Chunk M + Chunk

Gestures

3. Apply mental operators

HPK M +

KKKKKKKKKKKKKKK Helen of Troy:

356.34:

M +

KKKKKK M +

KLM: K M + K M + K M +

4. Add up the numbers

HMPK

0.4 + 1.35 + 1.1 + 0.2

3.05 sec =

Example: Date of birth

What's your pet way of collecting date of birth?

Facebook:

Yahoo:

Single masked

input field:

Facebook: 3 drop-downs

Click on month, select 'July'

MPK MPK

Click day, select '11'

MPK MPK

21 sec

Click year, scroll, wait, mouse off

MPK MP R MP (where R=1.0)

Select '1980'

MPK

Yahoo: Input, drop-down, input

Click day, type '11'

MPK HMKK

Click month, select 'July'

HMPK MPK

15.7 sec

Click year, type '1980'

MPK HMKKKK

Single masked input field

Click field, type '11'

MPK HMKK

Type '07'

MKK

8.7 sec

Type '1980'

MKKKK

Date of birth results

Single masked input field ~2.5 times faster!

21 sec

15.7 sec

8.7 sec

Happy GOMSing

You now know enough to start using KLM-

GOMS on your projects!

For more guidance I recommend Jef Raskin’s

“The Humane Interface”

Thanks!

@AndrewUX

designthinkage.com