HCI definitions part 2

Toggle - Switch from one effect, feature, or state to another by using a toggle.
Any instruction that works first one way and then the other;it turns something on the first time it is used and then turns it off the next time




Colour adds an extra dimension to an interface and can 
help the user understand complex information structures.
Colours can be used to highlight exceptional events.
If properly used it can:
- emphasize the logical arrangement of information,
- facilitate the discrimination of screen components,
- accentuate differences among elements and make displays
more interesting.


Colour Location
- In the centre of the visual field, use red and green.
- For peripheral viewing, use blue, yellow, black, and white.
- Use adjacent colours that differ by hue and value or lightness.




The 3 principal activities of software usability engineering
are:
- On-site observations of and interviews with system users, 
- Usability specification development, and 
- Evolutionary delivery of the system. 




How can you improve usability?
- Shortening the time to accomplish tasks,
- Reducing the number of mistakes made, 
- Reducing learning time, and
- Improving people's satisfaction with a system. 


Predictability - determining effect of future actions based on past interaction history.


Familiarity - how prior knowledge applies to new system.


Consistency - Likeness in input/output behaviour arising from similar situations or task objectives.


Generalizability - extending specific interaction knowledge to new situations.


Synthesizability - ability of the user to assess the effect of past operations on the current state. The user should see the changes of an operation. 


Architectural design - High-level description of how the system will provide the services required. 


Validation - designing the right product
Verification - designing the product right


Techniques for Prototyping
1. Storyboards
- Need not be computer based
- Can be animated
2. Limited functionality simulations
- Some part of system functionality provided by designers 
- Tools like HyperCard are common for these
- Wizard of Oz techniques 

Evaluation Techniques:
- Tests usability and functionality of system
- Occurs in laboratory, field and/or in collaboration with users
- Evaluates both design and implementation
- Should be considered at all stages in the design life cycle


Fixations: eye maintains stable position. Number and duration indicate level of difficulty with display.
Saccades: rapid eye movement from one point of interest to another
Scan paths: moving straight to a target with a short fixation at the target is optimal


Mistakes are errors in choosing an objective or specifying a method of achieving it whereas slips are errors in carrying out an intented method for reaching an objective. The division occurs at the level of the intention. A person established an intention to act. If the intention is not appropriate, this is a mistake. If the action is not what was intended, this is a slip. 


Gulf of execution is a term usually used in human computer interaction to describe the gap between a user's goal for action and the means to execute that goal.
This can be illustrated through the discussion of a VCR problem. Let us imagine that a user would like to record a television show. They see the solution to this problem as simply pressing the Record button. However, in reality, to record a show on a VCR, several actions must be taken:
Press the record button.
Specify time of recording, usually involving several steps to change the hour and minute settings.
Select channel to record on - either by entering the channel's number or selecting it with up/down buttons.
Save the recording settings, perhaps by pressing an "OK" or "menu" or "enter" button.
The difference between the user's perceived execution actions and the required actions is the gulf of execution.


Chunking is a term referring to the process of taking individual units of information (chunks) and grouping them into larger units. Probably the most common example of chunking is phone numbers. For example, a phone number sequence of 4-7-1-1-3-2-4 would be chunked into 471-1324. Chunking is often a useful tool when memorizing large amounts of information. By separating disparate individual elements into larger blocks, information becomes easier to retain and recall. 


I will upload all in a document whenever time permits.