ZULQUERNAIN MALLICK AJE Vol.9 2009 19-32
24
3. Results
Three experiments were conducted to study the effect of experience level on data entry task performance.
3.1. Experiment 1
In this experiment, the subjects of 48-62 years of age were tested for the data entry task performance under varying levels of vibration and textbackground color
combination Figure 3. Analysis of variance ANOVA Table 2 implied that the effects of vibration
and color combination of the text and background, and the interaction of these two factors, were statistically significant.
The significant interaction between the vehicular vibration level and the textbackground color combination necessitated an analysis of the simple main
effects; the result Table 3 indicated that level of vibration interacted significantly with textbackground color combination only at 0.85 ms
2
and 1.65 ms
2
for 48-62 year-old subjects in the real driving environment. However , the same was not true
in case of vibration level under the varying levels of textbackground color combination, i.e., black characters on white background and white characters on
black background. The mathematical relationship between NCEMWS for varying levels of vibration under the influence of particular textbackground color
combination was explored for subjects of age group 45-55 Years and the following models were obtained:
CE
B1
= 50.86 - 5.01V 2
CE
B2
= 68.72 - 8.24V 3
Where CE
B1
and CE
B2
represent characters entered per minute without spaces for textbackground color combinations B1black characters on white background and B2 white
characters on black background, and V is the value of vibration considered in this study 0, 0 .85 ms
2
and 1.65 ms
2
.
Table 2. Analysis of variance of vibration effects when operators 48-62 Years performed the
data entry task under varying levels of vibration and textbackground color combination.
Source of Variation SS
df MS
F
Between Subjects S 9
Within Subjects 50
A Vibration 1015.19
2 507.59
8.32 A x S Error I
1097.64 18
60.98 B Text background color
686.72 1
686.72 10.94
B x S Error II 564.75
9 62.75
A x B 660.20
2 330.10
6.02
Data entry task in mobile computing: effects of vibration, display colour, and user age
25
P er
for m
a nc
e i
n N
C EPMW
S
10 20
30 40
50 60
70 80
Vibration level
0.85 1.65
B1 B2
Figure 3. Comparison of operators performance in NCEPMWS for varying levels of
vibration and textbackground color combination for subjects of age group 48-62 Years B1: black character on white background, B2: white character on black background
20 40
60 80
100 120
Vibration level Pe
rf o
rm a
n c
e i
n N
C EPM
W S
0.85 1.65
B1 B2
Figure 4. Comparison of operators’ performance in NCEPMWS for varying
levels of vibration and textbackground color combination for subjects of age group of 33-47 Years. B1: black character on white background, B2: white Character on black background
Table 3. Analysis of Simple Main Effects when Subjects 48-62 Years Performed the Data
Entry task at varying levels of textbackground color combination under varying levels of equivalent vehicular vibration
Source of variation SS
Df MS
F B Textbackground color combination
At A1 vibration level 1 26.70 1 26.70 0.97
At A2 vibration level 2 138.20 1 138.20 5.02
At A3 vibration level 3 168.48 1 168.48 6.12
B x S Error 495.54 18 27.53
A Vibration Level At B1 White character on black background
35.42 2 17.71 0.87
3.2. Experiment 2
In this experiment, the 33-47 year-old subjects were tested for the data entry task performance under varying levels of vibration and textbackground color
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