Lecture Topics in HCI, by Saul Greenberg
Back to:	Task-Centered System Design

Exercise: Applying Task-Centered System Design

Your job is to perform a task-centered walkthrough of the prototype described below. Sample tasks are provided at the end of this page.

The Prototype

The system below is used by the Cheap Shop Department Store, a catalog-based store similar to Consumer's Distributors. Shoppers in the store decide on the item they want by browsing a paper catalog, and can then purchase items by entering the relevant information into the screens below.

Screen 1

Screen 2

Specifications

• To create an order
  • On screen 1, shoppers enter their personal information and their first order
  • text is entered via keyboard
  • the tab or mouse is used to go between fields.
• Further orders
  • shoppers go to the 2nd screen by pressing the Next Catalog Item button
• Order completion
  • shoppers select ‘Trigger Invoice’.
  • the system automatically tells shipping and billing about the order
  • the system returns to a blank screen #1
• To cancel order
  • Shoppers do not enter input for 30 seconds (as if they walk away)
  • The system will then clear all screens and return to the main screen
• Input checking
  • all input fields checked when either button is pressed.
  • erroneous fields will blink for 3 seconds, and will then be cleared.
  • the shopper can then re-enter the correct values in those fields.

Example Task Descriptions for "Cheap Shop"

Fred, who is caring for his demanding toddler son, buys an umbrella stroller (red is preferred, but blue is acceptable), pays for it in cash, and uses it immediately. Fred is a first-time customer to this store and has little computer experience.

An elderly arthritic woman is price-comparing the costs of a child's bedroom set, consisting of a wooden desk, a chair, a single bed, a mattress, a bedspread, and a pillow. She takes the description and total cost away with her, to check against other stores. Two hours later, she returns and decides to buy everything but the chair.

A "Cheap Shop" clerk, who is the sole salesperson in the store, is given a lengthy list of 10 items to order by a customer who does not want to use the computer. The items are: <list here>. After seeing the total, the customer decides to take all but the 4th and 6th item, and adds a new one to the list afterwards. The customer always changes their mind about paying by credit card, and decides to pay cash. The customer wants the items delivered to his home the day after tomorrow. While this is occurring, 6 other customers are waiting for the salesperson.

The Walkthrough Process

• Select one of the tasks scenarios
• For each user's step/action in the task:
  • can you build a believable story that motivates the user's actions?
  • can you rely on user's expected knowledge and training about system?
• if you can't:
  • tell a believable story about an action,
  • assume knowledge they would not have,
  • then you've located a problem in the interface!
• once a problem is identified, assume it has been repaired
• go to the next step in the task

Sample Walkthrough Template

Task number ____