Chapter 5

Question 1

method/methodology

Answer 1

the way an experiment is designed and carried
out.

Question 2

experiment design

Answer 2

the process of bringing together all the pieces necessary to test
hypotheses on a user interface or interaction technique.

Question 3

independent variable/factor

Answer 3

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.

Question 4

factorial experiments

Answer 4

Experiments designed with
independent variables

Question 5

dependent variable

Answer 5

a measured human behavior, The measurements depend on what the participant does.

Question 6

controlled variables

Answer 6

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.

Question 7

randomizing variables

Answer 7

randomizing variables.
There is a cost since more variability is
introduced in the measures, but there is a benefit since results are more generalizable.

Question 8

confounding variable

Answer 8

Any circumstance or condition that changes systematically with an independent variable

Question 9

reprentative tasks

Answer 9

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

Question 10

discriminative tasks

Answer 10

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.

Question 11

two conditions for applying results to people outside of the test range

Answer 11

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.

Question 12

usability evaluation/usability testing

Answer 12

These exercises often seek to assess a prototype system with users to determine problems with
the interface.

Not many people necessary to perform.

Question 13

Purposes of questionnaires

Answer 13

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.

Question 14

within-subject design/repeated measures

Answer 14

If each participant is tested on each level

Question 15

between-subject design

Answer 15

If each participant is tested on only one level, a separate group of participants is used for each test condition.

Question 16

practice/learner effect

Answer 16

the amount of practice increases systematically from one
condition to the next. (within-subject design)

Question 17

order/sequence effect

Answer 17

performance will worsen on
conditions that follow other conditions. This may follow from mental or physical fatigue—a
fatigue effect.

Question 18

counterbalancing

Answer 18

The compensatory ordering of
test conditions to offset practice effects

Question 19

Latin square

Answer 19

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.

Question 20

balanced latin square

Answer 20

latin square with different order to prevent sequence effects (ABDC instead of ABCD)

Question 21

group effect

Answer 21

differences
across groups in the mean scores on a dependent variable

typically due to
asymmetric skill transfer

Question 22

asymmetric skill transfer

Answer 22

differences in the amount of improvement, depending on the
order of testing.

Question 23

longitudinal study

Answer 23

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.