choice. Lastly, missing values were instances when some of the subjects gave no response or answers during the cued response tests. Between countries, Thailand had the most instances of missing values among all countries. Its missing values ranged from 2% to 23% across all 21 symbols. Sri Lanka was the opposite with no missing values in the cued response test. Missing values or subjects giving no answers as a parameter is a very good gauge of situations wherein the subjects did not know the answer because he/she couldn't understand the referent or the symbols presented. In actual user scenarios, this would be akin to the user not knowing which control would cause the target function ( Böcker, 1993).
Altogether, some both similarities and differences were noted regarding symbol understanding among Southeast Asian subjects. The results in the spontaneous identification and cued response tests in testing videophone symbols showed very low rates of correct identification and even correct association of the symbols across all countries. Differences between countries lie mostly in the levels of confusing the symbols from each other and their missing values. Both results showed the potential difficulties encountered by people from this region of recognizing and using these symbols. However, it is still believed that graphical symbols undeniably are still very useful. When conditions warrant that they be used alone or as a primary interface, user testing, adequate information, training as well as other help procedures become very important.
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