Karteikarten
SCC 202 - Predictive models
Karten in diesem Stapel (18)
- 1What is a model and what are they useful for?A simplification of reality.
Useful for designing, evaluating, predicting and/or
understanding behaviour. - 2What must a model be to be useful?To be useful, a model must be simpler than the behaviour it models (extremely complex models are of questionable value).
- 3What do predictive models simulate and why are they useful? Include the definition of term in your answer?Simulate user behaviour.
A task is decomposed into primitive actions.
Are useful as they allow human performance to be determined analytically rather than through time consuming experiments.
Allow designs to be explored hypothetically without requiring implementation. - 4Define GOMS model and it's components? First proposed in Card, Moran and Newell's 1983 book.
Components of the model:
Goals: that the users wish to accomplish (hierarchical).
Operators: Elementary acts (perceptual, motor, cognitive) that change the user’s mental state or task environment.
Methods: accomplish a goal by invoking Operators.
Selection rules: choose an appropriate method. - 5Underlying principle of the GOMS model?The rationality principle: users act rationally to attain their goals.
- 6Assumptions and variants of the GOMS model? Assumptions:
Does not consider interruptions or errors
Operators are not assumed to be concurrent (so only linear processes are
modelled)
Variants:
KLM
NGOMSL (Natural GOMS Language) - 7Define KLM model?Keystroke-Level Model
Simplest type of GOMS
Task execution time is predicted by the total time for elementary
keystroke-level actions.
Assumes an expert user - 8Describe the KLM process?1. Identify task
2. List the keystroke-level actions (operators) required to perform
the task
3. Insert mental operators for when the user has to stop and think
4. Look up the standard execution time for each operator
5. Add up the execution times for the operators
6. The total is the estimated time to complete the task - 9Operators and Times for KLM ?Image pg 16
- 10Define Fitts law?Models movement time for selection tasks
E.g. how long will it take me to select this button?
Originates from a 1D movement tasks (Fitts 1954)
The movement time for a well-rehearsed selection task:
Increases as the distance to the target increases.
Decreases as the size of the target increases. - 11State the Fitts law formula for movement time?MT = a + b x ID
MT = Movement Time
a is a constant (cognitive and motor preparation time)
b is a constant (measure of hand-eye co-ordination)
ID = log2(A/W + 1)
A is the ‘amplitude’ (distance to target) W is the ‘width’ (size) of target - 12How is accuracy recorded?Accuracy is also recorded through the error rate (how many times
you clicked without being inside the target) - 13What is fitts law often used to compare? What should you do if a device is worse than fitts law?Often used to compare input devices
If a new device performs worse than Fitts’ Law, you should throw it away. - 14What does steering law describe?Describes the time for cursor movement through a constrained path
or tunnel (Accot & Zhai, 1997) - 15What does Hick-Hyman Law for Choice Reaction describe?Time to select from a series of options when the user is optimally
prepared. - 16What does Power law of practice describe and when was it first proposed?Describes how task performance increases (i.e. takes less time) with
practise
First proposed by Newell & Rosenbloom (1981). - 17What does power law of practice apply to?Applies to simple and complex skilled behaviour tasks (from typing,
to reading text backwards, upside-down). - 18—
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- Karteikarten am SCC 202 - Predictive models, erstellt von Ayo Olutobi am 18/03/2017.
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