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The System Usability Scale (SUS) is a simple Likert scale and shares a comprehensive method to measure subjective assessments of the usability of interfaces. The approach for calculating the corresponding scores for SUS to measure the usability is defined by previous study (Brooke, 1996; Borsci, 2009; Bangor et al., 2009; Kortum, 2013). Different groups have various ideas regarding the usability of the map. For the text map with symbol-only and audio-only, the average SUS scores of Native English Speakers is larger than 70, and that of the text map of audio only is 82.5. By contrast, besides the text-free map with symbol and audio, the average SUS score of Illiterate people is much smaller than that of Native English Speakers and non-English Speakers. However, the SUS score for Illiterate people shows a significant increase in the text-free map with symbol and audio compared with the other four kinds of maps (from approximate 30 to 57.5). The SUS score between Native English Speakers and Non- English Speakers in text-free with symbol only is close (65 and 67.5). The average SUS score of each kind of maps is shown in Table-16, the detailed arithmetic for calculating the SUS is shown in Appendix L:

TABLE 17:SUSSCORES FOR DIFFER ENT PAR TIC IPANTS

Average Scores on each Map Participants Category/

Map Type Native English Speakers

Non-English Speakers Illiterate People

Text with Symbol Only 77.5(>70) 65 35

Text with Audio Only 82.5(>70) 45 22.5

Text-free with Symbol Only 65 67.5 37.5

Text-free with Audio Only 60 37.5 25

Text-free with Symbol and Audio

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8.4.1 Sign ifican ce T esting for Difference in S US S core

This section explores the difference between participant groups and their views of the usability of each kind of map. The main method used is to compare the significance of the difference between the SUS scores of different kinds of maps. The comparison is mainly focused on the text map with symbol-only and text-free map with symbol-only, text map with audio-only and text-free map with audio-only and three kinds of text-free maps. The statistical significant of the difference in SUS for compared maps is listed in Table-17, Table-18 and Table-19 and the detailed SUS scores for each map are listed in Appendix M. The highlighted row is the only one that has a significance difference. Corresponding measuring methods are shown in Appendix M.

TAB LE 18:SIGN IF IC ANT DIF FER E NCE OF SUS SCO RE –NAT IVE EN G LISH SPE AK ER S

Native English Speakers

Text with Symbol-only &

Text-free with Symbol-only

F P-value F crit

7.352941 0.053447 6.607891

Text with Audio-only &

Text-free with Audio-only

F P-value F crit

45 0.001114 6.607891

Text-free with Symbol-only &

Text-free with Symbol and Audio

F P-value F crit

0.251509 0.637311 6.607891

Text-free with Audio-only &

Text-free with Symbol and Audio

F P-value F crit

72

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TAB LE 19:SIGN IF IC ANT DIF FER E NCE OF SUS SCO RE –NON-ENG LISH SPE AKER S

Non-English Speakers

Text with Symbol-only &

Text-free with Symbol-only

F P-value F crit

0.9375 0.377391 6.607891

Text with Audio-only &

Text-free with Audio-only

F P-value F crit

3.648649 0.114365 6.607891

Text-free with Symbol-only &

Text-free with Symbol and Audio

F P-value F crit

2.410714 0.181214 6.607891

Text-free with Audio-only &

Text-free with Symbol and Audio

F P-value F crit

86.78571 0.00024 6.607891

TAB LE 20:SIGN IF IC ANT DIF FER E NCE OF SUS SCO RE –ILLITE R ATE PEOP LE

Illiterate People

Text with Symbol-only &

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Text-free with Symbol-only 5.136986 0.072758 6.607891

Text with Audio-only &

Text-free with Audio-only

F P-value F crit

5.95 0.061482 6.607891

Text-free with Symbol-only &

Text-free with Symbol and Audio

F P-value F crit

23.52 0.004675 6.607891

Text-free with Audio-only &

Text-free with Symbol and Audio

F P-value F crit

68.51351 0.00042 6.607891

For native English speakers, there is no significant difference of SUS Scores between “text map with symbol-only” and “text-free map with symbol-only” (F (7.352941)> F (6.607891), P-value (0.0053) >

0.005)), whereas the difference of SUS Scores between “text map with audio-only” and “text-free map with audio-only” is significant. For non-English speakers, the significant differences of SUS

Scores only exist in “text-free map with audio-only” and “text-free map with symbol and audio”. However, in terms of Illiterate people, significant differences only exist between “text-free map with symbol-only” and other text-free maps. Both have a significant difference of SUS scores compared

with “text-free map with symbol and audio” respectively.