Le loi de Fitts
Le loi de Fitts Le loi de Fitts
loi de fitts eee & gef 459 engineering human-computer interaction © greg phillips royal military college of canada unlimited use permitted within the government of canada other uses subject to conditions of a creative commons license http://creativecommons.org/licenses/by-nc/3.0/ 1
- Page 2 and 3: 1. Toolbars offer the user the opti
- Page 4 and 5: 3. A right-handed user is known to
- Page 6 and 7: 5. Explain why a Macintosh pull-dow
- Page 8 and 9: 7. Give at least one advantage circ
- Page 10 and 11: 9. Apple’s industrial designers m
- Page 12 and 13: fitts’s law (fitts, 1954, mackenz
- Page 14: fitts’s constant ‘b’ device b
<strong>loi</strong> <strong>de</strong> fitts<br />
eee & gef 459<br />
engineering human-computer interaction<br />
© greg phillips<br />
royal military college of canada<br />
unlimited use permitted within the government of canada<br />
other uses subject to conditions<br />
of a creative commons license<br />
http://creativecommons.org/licenses/by-nc/3.0/<br />
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1. Toolbars offer the user the option of<br />
displaying a label below each tool.<br />
Name at least one reason why<br />
labelled tools can be accessed faster.<br />
(Assume, for this, that the user<br />
knows the tool and does not need the<br />
label to i<strong>de</strong>ntify the tool.)<br />
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2. Dans un logiciel <strong>de</strong> graphisme, vous<br />
avez un palette d’outils qui se<br />
consiste d’un matrice d’icônes<br />
16⨉16 pixels organisé comme<br />
illustré. Si les icônes doivent rester a<br />
gauche <strong>de</strong> l’écran et vous ne pouvez<br />
pas modifier leur gran<strong>de</strong>ur, qu’est-ce<br />
que vous pouvez faire pour baisser le<br />
temps moyen d’accès <strong>de</strong>s outils<br />
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3. A right-han<strong>de</strong>d user is known to be<br />
within 10 pixels of the exact centre<br />
of a 1600 X 1200 screen. You will<br />
place a single-pixel target on the<br />
screen that the user must point to<br />
exactly. List the five pixel locations<br />
on the screen that the user can<br />
access fastest. For a bonus point, list<br />
them in or<strong>de</strong>r from fastest to slowest<br />
access.<br />
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4. Dans Windows, il y a une barre <strong>de</strong><br />
tâches qui peut être cachée, ou<br />
visible en permanence. Si c’est<br />
caché, on peut le révéler en touchant<br />
le curseur au pied <strong>de</strong> l’écran.<br />
Donnez au moins <strong>de</strong>ux raisons pour<br />
lesquelles cette approche est très<br />
inefficace.<br />
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5. Explain why a Macintosh pull-down<br />
menu can be accessed at least five<br />
times faster than a typical Windows<br />
pull-down menu. For a bonus point,<br />
suggest at least two reasons why<br />
Microsoft ma<strong>de</strong> such an apparently<br />
stupid <strong>de</strong>cision.<br />
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6. En navigant un menu hiérarchique,<br />
quel aspect <strong>de</strong> la navigation<br />
contribue le plus au temps total <strong>de</strong><br />
navigation Point <strong>de</strong> bonus: sans<br />
restructuration du menu, qu’est ce<br />
qu’on peut faire pour améliorer la<br />
vitesse d’usage<br />
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7. Give at least one advantage circular<br />
popup menus have over standard,<br />
linear popup menus.<br />
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8. Qu’est-ce qu’on peut faire pour<br />
mettre plus en équilibre le temps<br />
moyen d’accès pour un menu<br />
contextuel linéaire, sans<br />
réorganisation <strong>de</strong>s options sur le<br />
menu<br />
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9. Apple’s industrial <strong>de</strong>signers<br />
managed to screw up an otherwise<br />
won<strong>de</strong>rful keyboard to save a very<br />
small amount of space. What’s wrong<br />
with the keyboard and why is this so<br />
incredibly stupid<br />
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10. Toutes les réponses primaires à ces<br />
questions ont quelque chose en<br />
commun. Qu’est ce que c’est<br />
la <strong>loi</strong> <strong>de</strong> fitts!<br />
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fitts’s law<br />
(fitts, 1954, mackenzie, 1991)<br />
start<br />
point<br />
target<br />
A<br />
W<br />
MT = a + b·log 2 (A/W + 1)<br />
MT = “movement time”<br />
log 2 (A/W + 1) = “in<strong>de</strong>x of difficulty”<br />
a = “startup time” in sec<br />
} b = “1/speed” in sec/bit<br />
<strong>de</strong>vice specific<br />
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fitts en 2D<br />
A<br />
(mackenzie & buxton, 1992)<br />
utiliser quoi<br />
comme «gran<strong>de</strong>ur»<br />
du cible<br />
target<br />
W’<br />
W W<br />
H<br />
W’<br />
H<br />
W+H<br />
W·H<br />
min(W, H)<br />
par expérience, W’ ou min(W, H)<br />
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fitts’s constant ‘b’<br />
<strong>de</strong>vice b -1<br />
hand 10.6<br />
mouse 10.4<br />
joystick 5.0<br />
trackball 2.9<br />
touchpad 1.6<br />
b -1 (or 1/b) is<br />
the “information<br />
processing<br />
speed” of the<br />
<strong>de</strong>vice<br />
eyetracker 13.7<br />
MT = a + b·log2(A/W + 1)<br />
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