Keystroke Level Model (KLM-GOMS)

GOMS and KLM used to model the user interaction. GOMS stands for Goal, operator, methods and selections rules. GOMS depends on HTA. One the other hand, KLM is a refinement for GOMS that it aims to show how long task will take. In this blogpost I will workout this assuming the following:

 Expert user types "hello, world" in word processor and change the text to 18point Arial font.

GOMS

Goal: Typing "hello, world" and change the font.

Operators: Mouse , touchpad or touchscreen , Keyboard either physical or on screen. 

Methods: Type "hello, World" , select the text, move the mouse to the font options or using the keyboard shortcut.  

Selection rules: If there is no mouse expert user will be resourceful to use keyboard shortcuts.So we can assume the mouse will not be used and will examine if the word processor offer this options for the expert user.

Note: I will disregard Touchscreen in the example assuming user work on a PC.

 

 HTA

 0- Write "Hello, World" (12 character)

1- Use shift+arrows keys to select the text

2- press on shift+] keys to maximise the font to 18points

3- Use the mouse to the main menu and choose Arial font

KLM

Assuming each key stroke takes 0.08 s , moving from keyboard to the mouse 0.40 s , clicking on mouse 0.20s , mental preparation could be 1.20 s needed after typing and when user prepare him/her self to format the text. 

Therefore, TotalTime = Keystrokes( 0.08 * 12 ) + SelectText(0.08*12) + MaxmizeFont(0.08*6) + MentalPreparation (1.20) + Clicks(0.20*2) + MovingMouse (2 s)+ DealWithFontMenu(2s)

= 0.96 +  0.96 + 0.48 + 1.20 + 0.4 + 2 + 2 

= 8 seconds ! 

I doubt this result , but could be for  an expert users ... 

However, this method can be tricky and not reflect the potential of interfaces that deliver various options to do the tasks. So when we compare between two interfaces maybe one interface deliver best interaction that can be accessed using different steps that the other interface doesn't support.Thus, I think we should be aware and consider all the factors when we use this method to compare.