Cognitive Walkthrough with Dillon Mills

To evaluate our prototype, I sat down with Dillon Mills (after reading Think Like A Persona) to perform a cognitive walkthrough. This will help us understand any usability issues with the steps needed to complete a given task.

The task in this case is to buy the basics – bread, milk and eggs. The following steps Dillon wants to take are:

1. Find the relevant section of the supermarket (bakery, dairy products, etc.)
2. Make an informed and comfortable decision about a product to purchase.
3. Buy further items in this particular section or navigate to another section of interest.
4. On completing the task, purchase and receive the goods.

The steps needed in the prototype to complete this task are:

1. Turn on the device (by pressing any button)
2. Watch a introduction given by Terry Wogan
3. Confirm with the system whether they know how to use the system or not.
4. Either watch the tutorial by pressing the ‘Play’ button on the next screen or be presented with the main menu for the system.
5. Indicate that Dillon wants to perform a new shop.
6. Navigate to a section of the supermarket by pressing the coloured button which corresponds to the desired area (for example, the bakery)
7. Push the handles on the device forward to navigate towards the desired group of products (loafed bread)
8. Select the product they want by browsing through the products
9. Make a selection by pressing ‘buy’, or viewing more info by pressing ‘info’.
10. Navigate back to the shop layout and repeat the process for each section.
11. Purchase the products by pressing the buy. (not implemented yet)

I found that it would be extremely tedious to go through each of these stages and perform a detailed evaluation of their usability. However, I have picked one to demonstrate the thought process involved:

Step 9: Making a selection by pressing buy.

Will the users be trying to produce whatever effect the action has?

By pressing the ‘buy’ button, the user will change the state of the shopping cart – adding the product currently focused. Although the word 'buy' itself does not directly indicate ‘adding to a cart’, Dillon had no problem making this distinction.

Will users be able to notice that the correct action is available?

When a system is focused upon on product, the option to ‘buy’ in the form of a butto will always be available.

Once users find the correct action at the interface, will they know that it is the right one for the effect they are trying to produce?

Since there are only five options, there is a one in five chance that Dillon will make a mistake. When focusing on a product, there are no similar functions which the ‘buy’ button represents. It is fairly clear to Dillon that ‘buy’ involves purchasing and the other buttons have no relation to this task.

After the action is taken, will users understand the feedback they get?
Dillon was given no feedback that the item was added to the shopping cart. This confused him slightly as everything suddenly disappeared - and he was presented with the store menu. The only indication that an item was added as it has now appeared in the ‘shopping cart’ list.