Simple Example of a Cognitive Walkthrough

Here is a first cut of a walkthrough (of a first part of a task):

The user wants to write a letter, using a new PC.
She knows the PC needs to be turned on.
So she pushes the power button.
...

This story is not believable for the following reasons:

The user may think that the PC is always turned on. The user may also look at the screen and notice it is dark and therefore think the computer is off, while maybe only the screen is not turned on, or maybe the screen is dark because it is in a power-save mode.

It may or may not be part of the user's general knowledge of PCs that a PC makes (fan) noise when turned on. A user switching from a diskless (and fan-less) workstation or X-terminal to a PC may not expect to hear noise.

When the user finally really figures out that the PC is not turned on, she has to locate the power switch first. It may be on the front of the computer case, or on the back, or there may even be a switch on the front and on the back. None of these switches may be marked with "Power" or with "On/Off" or anything else that is recognizable. There may be several switches in the front which look identical, are not labeled, and one of which is "Power", one is "Turbo" and one is "Speaker on/off". There are some PCs with a switch in the back, with "0" and "1", which has to be switched to "1", and which then requires the user to press another switch in the front to really power up the PC.

When the problems with this first action are identified you may assume they are fixed (and write down how to fix them) and then you can proceed with the next action.