The button that did nothing
Sam uses a canteen order app (made up). He taps "Order". Nothing seems to happen. He taps again, and again. Later he finds he has ordered five lunches.
The app worked. But it did not tell him it had worked. That is a usability fault, and it cost Sam four lunches. This lesson shows what to look for.
By the end of this lesson
Note
I can assess how usable an app is, using clear usability features.
Key words
| Word | What it means |
|---|---|
| Usability | how easily and quickly people reach their goal in an app |
| Feedback | a sign that the app has done what you asked |
| Consistency | the same thing looks and works the same way everywhere |
| Validation | a check that what was typed is sensible |
| Accessibility | how well people with different needs can use it |
| Input control | a part of the screen where the user gives information |
The cells students fill in are left blank in this preview.
Starter: what you already know
Have a go
Starter: what you already know
4 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Six features make an app usable
Usability means how easily and quickly people reach their goal. Six features show it. Visibility: the user can see what they can do. Control: they can go back and undo. Feedback: the app answers every action.
Consistency: things look and work the same way. Error prevention: the app stops mistakes before they happen. Flexibility: beginners and experts can both work well.
Six usability features in the canteen app
| Feature | Good example | Poor example |
|---|---|---|
| Visibility | The Order button is easy to see | Ordering hides behind a tiny icon |
| Control | A Cancel button until you pay | No way to undo an order |
| Feedback | A message: Order sent | Nothing happens after the tap |
| Consistency | All buttons look the same | Each screen has a new style |
| Error prevention | Asks: Order 5 lunches? | Lets you order 500 by accident |
| Flexibility | Repeat last order, for regulars | Every order starts from nothing |
The cells students fill in are left blank in this preview.
Check
Have a go
Check
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.