Our results measure the time for participants to correctly enter a predetermined message on a cellular phone using either the standard keypad or T9 predictive text entry. At the end of the experiment, participants were asked to fill out a subjective survey rating their impressions of the text entry method. We found that times to correctly enter the messages using the T9 text entry method were statistically significant. Times were shorter for those who used the T9 input method than those using standard keypad entry.

Performance Time

Figure 1: Comparison of Mean Times to Correct completion.

The dependant variable measured in the experiment is the text input method used. We used a t-test to compute the statistical significance of our results. This showed that the difference in the mean times between those subjects who used T9 versus those using standard keypad entry were statistically significant. The t-tests were calculated with an unequal variance measurement and with both one and two-tail distributions as displayed in table 1.

Table 1: Analysis of Completion Times

Subjective Satisfaction

Participants completed a subjective evaluation of their impressions after completing the text entry task. Impressions were recorded for questions pertaining to: general experience, time to mastery, likeliness to purchase a comparable phone, encouragement to use the technology, and frustration level. Results were not found to be statistically significant.

User Satisfaction

Figure 2: User Satisfaction.

Table 2: Subjective Satisfaction