Lec6 - Input Models

Question 1

What do you need to remember for calculating Fitts law?

Answer 1

-Distance is from cursor to centre of button
-Width is in the direction of movement

Question 2

What are the differences between pointing and crossing?

Answer 2

Pointing
-Control and correction at the end of the movement only
-Crossing object boundary and stopping on object (button)
-Distance to middle of button

Crossing
-Control and correction all the way to the goal
-Crossing through means selecting so no need to stop on object (e.g. a line)
-Distance to the boundary
-Width is how long it is

Question 3

What are some advantages to cross-based selection?

Answer 3

-Multi-selection: can move across multiple objects to select them
-Good for input devices with no buttons to click
-Good for pens/stylus as you don’t need to lift pen
-Good when movement jittery (e.g. hand tremors)

Question 4

What are the fastest and most accessible points?

Answer 4

Corners and edges

Cant overshoot

Question 5

What is steering law (formula) and when would it be applied?

Answer 5

-MT = a + b * D/W (or *ID as ID = D/W)

• Used to acquire a target through a tunnel (e.g. drop downs with side bars - multi-level drop-downs - these use steering law when moving sideways but Fitts law when moving down)

Question 6

What is KLM?
What are the types of execution?

Answer 6

-Set of basic input operators with time estimates for their execution

Physical
-Pressing key
-Pointing mouse

Mental
-Preparation to perform a motor action
-Time to make a decision or to look for something

System response
-Time the user must wait for a response

Question 7

What are some advantages to KLM

Answer 7

Advantages
-Easy to apply - simple model
-Can be carried out using sketches of a UI
-Accurate
-Appropriate for routine tasks
-Useful to compare differing UIs
-Good for testing designs for frequent and repetitively used UIs

Question 8

What are some limitations to KLM?

Answer 8

Limitations
-Assumes the user is an expert and the task well-rehearsed
-Assumes error-free operation
-Not appropriate for tasks involving exploration or reasoning