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User Assessment of Standard and Reduced-Size Numeric Keypads

Authors:
David F. Loricchio
David F. Loricchio
David F. Loricchio
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James R. Lewis at MeasuringU
James R. Lewis
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Abstract

As technology improves, portable computers become smaller and more compact. A clear design challenge is to provide a system that is as compact as possible without degrading system usability. The keyboard is still the primary input device for compact computers. Previous research has indicated that reduced key spacing adversely affects skilled typing. Therefore, a portable computer system should provide a keyboard with full-sized keys in the primary typing area. The purpose of this study was to determine if reducing key size and spacing adversely affects the usability of a numeric keypad. Skilled keypad operators compared a standard-size numeric keypad to two keypads that had reduced center-to-center key spacing. One of these keypads achieved its reduction primarily by reducing the key spacing. The other reduced both key size and spacing. (Note that the small changes in key size and spacing have little effect on the overall device dimensions of a numeric keypad.) Operators typed numbers faster with and preferred the standard keypad over the keypad with both reduced key size and key spacing. If a numeric keypad is offered as part of a portable computer, every effort should be made to provide full-sized keys. If reduced key spacing is unavoidable, wide keys are preferable to narrow keys.
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PROCEEDINGS
of
the
HUMAN
FACTORS
SOCIETY
35th
ANNUAL
MEETING-1991
USER ASSESSMENT OF STANDARD AND REDUCED-SIZE NUMERIC KEYPADS
David F.
Loricchio
James
R.
Lewis
International
Business
Machines,
Corp.
Boca Raton, FL
As
technology
improves,
portable
computers
become
smaller
and
more
compact. A
clear
design
challenge
is to
provide
a
system
that
is as
compact
as
possible
without
degrading
system
usability.
The
keyboard
is
still
the
primary
input
device
for
compact
computers.
Previous
research
has
indicated
that
reduced
key spacing
adversely
affects
skilled
typing.
Therefore, a
portable
computer
system
should
provide
a
keyboard
with
full-sized
keys in
the
primary
typing
area. The
purpose
of
this
study
was to
determine
if
reducing
key
size and
spacing
adversely
affects
the
usability
of a
numeric
keypad.
Skilled
keypad
operators
compared
astandard-size
numeric
keypad to
two
keypads
that
had
reduced
center-to-center
key spacing. One of
these
keypads
achieved
its
reduction
primarily
by
reducing
the key
spacing. The
other
reduced
both
key
size and spacing. (Note
that
the
small
changes
in
key
size and
spacing
have
little
effect on
the
overall
device
dimensions
of a
numeric
keypad.)
Operators
typed
numbers
faster
with and
preferred
the standard keypad
over
the
keypad
with
both
reduced
key
size and key spacing. If a
numeric
keypad is offered as
part
of a
portable
computer,
every
effort
should
be made to pi
uvide
full-sized
keys. If
reduced
key
spacing is
unavoidable,
wide
keys
are
preferable
to
narrow
keys.
OBJECTIVE
The
objective
of
this
study
was to
determine
if a
numeric
keypad
could
be
reduced
in size
without
degrading
the
performance
of
the
keypad for
skilled
keypad
operators.
As
technology
improves,
portable
computers
become
smaller
and
more
compact. A
clear
design
challenge
is to
provide
a
system
that is
as
compact
as
possible
without
degrading
system
usability.
The
keyboard
is
still
the
primary
input
device
for
compact
computers.
Previous
research
has
indicated
that
reduced
key
spacing
adversely
affects
skilled
typing.
Kennedy
and
Loricchio
(1987)
compared
standard
and
reduced-size
keyboards.
The
standard size
keyboard
had 19 mm
spacing
in both the
horizontal and
vertical
dimensions.
The
reduced
size
keyboard
had 19 mm
horizontal
spacing and 15 mm
vertical
spacing. The
keyboards
were
identical
except
for
the
difference
in vertioal key spacing.
Although
there
were
no
significant
differences
in
typing
speed
or
error
rate,
users
significantly
preferred
the
keyboard
with
19 mm
spacing
over
the
keyboard
with
15 mm spacing.
They
indicated
that
they
believed
that
the
full-size
keyboard
was
easier
to use and was
the
keyboard
they
would
choose
to
purchase.
This
research
(Kennedy
and
Loricchio,
1987)
indicated
that
a
portable
computer
system
should
provide
a
keyboard
with
full-sized
keys in
the
primary
typing
area. Based on
this
information,
it is
reasonable
to
hypothesize
that
reducing
the
size of
the
numeric
keypad
would
show
similar
results.
Because
there
are
relatively
few
keys on a
numeric
keypad,
small
reductions
in key size and spacing of a
numeric
keypad do not
result
in
very
large
reductions
in
the
overall
dimensions
of
the
device.
However,
if
the
reductions
have no effect on
user
performance
or
preference,
then
the
reduction
in
key
spacing
and size
251
would
help
the
design
goal of
making
the
portable
as
compact
as
possible.
The
purpose
of
this
study
was
to
determine
if
reducing
key size and
spacing
adversely
affects
the
usability
of a
numeric
keypad.
To
test
this
hypothesis,
skilled
keypad
operators
compared
three
commercially
available
numeric
keypads.
METHOD
Participants
Fifteen
participants
were
recru
ited
from
a
temporary-help
employment
agency. All but
one
participant
had
experience
using
spreadsheet
applications
on a
computer.
Experience
with
spreadsheets
ranged
from
two
months
to
more
than
four
years. Six had
more
than
four
years of
experience,
five had
from
one
to
three
years
experience,
and
three
had
less
than
one
year
of
experience.
Seven
participants
had
college
degrees,
six had
completed
some
college
courses,
and
two
had
high
school
education.
All
participants
said
they
could
use a
numeric
keypad
without
looking at
the
keys.
Keypads
The
layout
of
the
numeric,
add, and
clear
keys
was
the
same
on all
three
keypads.
These
were
the
only
keys used by
the
participants.
Table 1
shows
the
key
size
and
spacing
for
these
keypads. The
keypads
were
categorized
by
two
characteristics:
center-to-center
key
spacing (18 mm or 16 rnrn); and
width
of the
key
cap
(wide
or narrow). The
keypads
are
referred
to as "18" (18 rnrn spacing), "16W" (16 rnrn
at HFES-Human Factors and Ergonomics Society on December 21, 2015pro.sagepub.comDownloaded from
PROCEEDINGS
a/the
HUMAN
FACTORS
SOCIETY
35th
ANNUAL
MEETING-I991
spacing,
wide
keys), and "16N" (16 mm spacing,
narrow
keys). Table 3.
Mean
Input Rate (keystrokes/minute)
Table 1.
Key
Dimensions
Multiple
Comparisons
18
keypad
16W
keypad
16N
keypad
Note:
Means
connect.ed
by a
line
are
not.
significantly
different
at the .85
level.
Key
spacing
Key
size
Keypad
Horiz. Vert.
Width
11eight
18 18 15 14 10
16W
16 12
14
9
16N
16 15 18 10
79.75 76.18 73.29
CONCLUSIONS
Note:
Means
connected by a
line
are not
significant.ly
different
at the .05
level.
Multiple
Comparisons
16\~
keypad
18
keypad
16N
keypad
Table 4.
Mean
Error Rate
(incorrect
calculat.ions/minute)
0.15
0.29
0.33
Pairs of Latin
squares
(Lewis, 1989)
were
used
to
counterbalance
the
order
in
which
the
participants
used the
keypads
and
stimulus
sets. Participants
received
five
minutes
of
practice
on each keypad.
Each
participant
used all
three
keypads
to add a set of
numbers.
Each set
consisted
of 100
five-digit
numbers.
The
numbers
were
arranged
in 25
rows
with
four
numbers
in each row. The
participants'
task
was to add
the
four
numbers
in each
row
and to
write
the
sum in
the
space
beside
each row.
Participants'
scores
were
the
number
of
sums
calculated
during
a
seven-minute
period.
After
completing
the
addition
task with all
three
keypads,
participants
ranked
the
keypads
in
order
of
their
preference.
Procedure
RESUL1S AND DISCUSSION
Tables 2, 3 and 4
show
the
results
for the
dependent
variables
of
preference,
input
rate, and
error
rate. A
Friedman
test
(Hollander
and Wolfe,
1973)
indicated
a
significant
difference
in
preference
among
the
keypads
(X
2(2)
=8.93, P<.05).
Distribution-free
muItiple
comparisons
based on
the
rank
sums
(Hollander
and Wolfe, 1973)
showed
that
the
18 keypad was
significantly
preferred
over
the 16N
keypad (p <.05).
Analyses
of
variance
were
used to
analyze
typing
speed
and
errors.
Keypad
type
had a
significant
effect on
typing
speed
(F(2,14) =3.02,
P<0.06). Participants
typed
significantly
faster
with
the
18 keypad than
with
the 16N keypad (Duncan
range
test, p<.05).
There
were
no
significant
differences
in
error
rates (F(2,14) =1.96,
p=0.16).
Skilled
keypad
operators
compared
a
standard-size
numeric
keypad to
two
keypads
that
had
reduced
center-to-center
key spacing. One of
these
keypads
achieved
its
reduction
primarily
by
reducing
the
key
spacing. The
other
reduced
both key size and
spacing. (Note
that
small
changes
in key size and
spacing
have
little
effect on the
overall
device
dimensions
of a
numeric
keypad.)
Operators
typed
numbers
faster
with and
preferred
the
standard
keypad
over
the
keypad
with
both
reduced
key
size
and key spacing. If a
numeric
keypad is offered as
part
of a
portable
computer,
every
effort shouId be
made
to
provide
full-sized keys. If
reduced
key
spacing
is
unavoidable,
wide
keys are
preferable
to
narrow
keys.
REFERENCES
Table 2.
Mean
Preference
Ranks
MUltiple
Comparisons
18
keypad
16W
keypad
16N
keypad
Note:
Means
connected by a
line
are not
significantly
different
at the .05
level.
1.40 2.13 2.47
Kennedy, P.J., and Loricchio, D.F. (1987). Key space
and
user
productivity.
In
Abridged
Proceedings
of
Poster
Sessions of the
Third
International
Conference
on
Human-Computer
Interaction
(page
48).
New
York, N.Y.: Elsevier.
Hollander, M. and Wolfe, D. A. (1973).
Nonparametric
statistical methods.
New
York, NY:
John
Wiley.
Lewis, J.R. (1989). Pairs of Latin
squares
to
counterbalance
sequential
effects and
pairing
of
conditions
and
stimuli.
In
Proceeding
of the Human
Factors
Society
33rd
Annual
Meeting,
Santa
Monica,
CA: Human Factors Society.
252
at HFES-Human Factors and Ergonomics Society on December 21, 2015pro.sagepub.comDownloaded from
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... Although factors other than lateral pitch may have influenced the preferences for the 12 mm and 13 mm lateral pitches, these results are consistent with a study of standard and reduced sized numeric keypads by Loricchio (1991). In this study, participants preferred keypads with a greater lateral pitch (center-to-center key spacing) over keypads with a smaller lateral pitch. ...
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Key space and user productivity. In (page 48)
  • P J Kennedy
  • D F Loricchio