Chapter 5 Flashcards
method/methodology
the way an experiment is designed and carried
out.
experiment design
the process of bringing together all the pieces necessary to test
hypotheses on a user interface or interaction technique.
independent variable/factor
a circumstance or characteristic that is manipulated or systematically controlled to a change in a human response while the user is interacting with
a computer.
there is
nothing a participant can do to influence an independent variable.
factorial experiments
Experiments designed with
independent variables
dependent variable
a measured human behavior, The measurements depend on what the participant does.
controlled variables
variables that might interfere or influence a participant are controlled. Controlling them means that they are fixed at a nominal
setting during the experiment so they don’t interfere.
Having lots of control variables reduces the variability in the measured
behaviors but yields results that are less generalizable.
randomizing variables
randomizing variables.
There is a cost since more variability is
introduced in the measures, but there is a benefit since results are more generalizable.
confounding variable
Any circumstance or condition that changes systematically with an independent variable
reprentative tasks
A good task
is representative of the activities people do with the interface. A task that is similar to actual
or expected usage will improve the external validity of the research–the ability to generalize
results to other people and other situations.
While using a task that is representative of actual usage may improve external validity, the
downside is a decrease in internal validity
discriminative tasks
A good task is also one that can discriminate the test conditions. A good task must attune to
the points of differentiation in order to elicit behavioral responses that expose benefits or
problems among the test conditions. This should surface as a difference in the measured
responses across the test conditions. A difference might occur if the interfaces or interaction
techniques are sufficiently distinct in the way the task is performed.
two conditions for applying results to people outside of the test range
First, the people actually tested must be members of the same population of
people to whom results are assumed to hold.
Second, a sufficient number of participants must be tested.
usability evaluation/usability testing
These exercises often seek to assess a prototype system with users to determine problems with
the interface.
Not many people necessary to perform.
Purposes of questionnaires
One is to
gather information on demographics (age, gender, etc.) and experience with related
technology. Another is to solicit participants’ opinions on the devices or interaction tasks with
which they are tested.
within-subject design/repeated measures
If each participant is tested on each level
between-subject design
If each participant is tested on only one level, a separate group of participants is used for each test condition.
practice/learner effect
the amount of practice increases systematically from one
condition to the next. (within-subject design)
order/sequence effect
performance will worsen on
conditions that follow other conditions. This may follow from mental or physical fatigue—a
fatigue effect.
counterbalancing
The compensatory ordering of
test conditions to offset practice effects
Latin square
In the simplest case of a
factor with two levels, say, A and B, participants are divided into two groups. If there are 12
participants overall, then Group 1 has 6 participants and Group 2 has 6 participants. Group 1
is tested first on condition A, then on condition B. Group 2 is given the test conditions in the
reverse order
an n ×
n table filled with n different symbols (e.g., A, B, C, and so on) positioned such that each
symbol occurs exactly once in each row and each column.
balanced latin square
latin square with different order to prevent sequence effects (ABDC instead of ABCD)
group effect
differences
across groups in the mean scores on a dependent variable
typically due to
asymmetric skill transfer
asymmetric skill transfer
differences in the amount of improvement, depending on the
order of testing.
longitudinal study
An experimental evaluation where participants practice
over a prolonged period
In many situations, the goal of a longitudinal study is to compare the viability of a new
technique against current practice.
