updated 09:15 pm EST, Tue November 13, 2007
iPhone input not perfect
While many believe that experience improves the iPhone typing accuracy, a new study found that more experience does not generally improve texting error rates for iPhone users and also indicates that iPhone owners generally perform worse than their numeric phone or QWERTY-device counterparts. The study did find that iPhone owners entered text as rapidly as those with QWERTY devices, but that error rates of iPhone users were significantly higher. After studying iPhones users who had their device more than 30 days, the Chicago-based usability consultancy User Centric found that texting errors on the iPhone were significantly more than both numeric- and QWERTY-based devices. The study concluded that "compared to hard-key QWERTY devices, the iPhone may fall short for consumers who use on their mobile device heavily for email and text messaging."
The company noted that the iPhone’s predictive and corrective text features do alleviate some of the errors users make while texting, but it does not catch them all.
"While the iPhone's corrective text feature helps, this data suggests that iPhone users who have owned the device for a month still make about the same number of errors as the day they got it," said Gavin Lew, Managing Director. "iPhone is a great switch from a numeric phone. But if you're switching from a hard-key QWERTY phone, try the iPhone in the store first."
The firm had previously found that test participants found the iPhone's touch keyboard overly sensitive despite the iPhone's overall high usability; however, its new usability study compared texting experiences of iPhone owners and non-owners across devices.
iPhone owners, the study found, made significantly more texting errors on their own phone -- an average of 5.6 errors/message) -- than both QWERTY owners (2.1 errors/message) and numeric phone owners (2.4 errors/message) on their own phones.
Interestingly, comparing texting performance between iPhone owners and novices (non-owners) on the iPhone found no significant difference in error rates.
The firm said it collected data from 60 participants who entered specific text messages and completed mobile device tasks, including 20 iPhone owners (who owned for more than a month), 20 hard-key QWERTY phone (aka QWERTY) owners, and 20 numeric phone owners (multi-tap texters) all entered six fixed-length text messages on their own phones. Non-iPhone owners also entered six messages on a test iPhone and a phone of another type (the Blackberry was the other phone for numeric users while QWERTYs used a Samsung E300).
Unfamiliar Users Performed Best on Hard-Key QWERTY Phone
User Centric said also compared users' performance on unfamiliar phones and found -- as would be expected -- that numeric phone owners had faster text entry on a hard-key QWERTY phone than on the iPhone; they also made significantly fewer errors on the hard-key QWERTY devices.
"Participants also indicated a preference for hard-key QWERTY phones when texting," said Jen Allen, User Experience Specialist. In addition, the iPhone still lacks some critical texting features, such as the ability to forward texts to others and the ability to send the same text to multiple recipients. Apple's three software updates since the release in July have not addressed these issues.
Hit rates and False Alarm Keys
Interesting, the study found that the hit rates (i.e., the percentage of time the desired key was pressed) for all keys on the iPhone keyboard were consistently 90 percent or higher, but much lower than the 97 percent for all keys on a QWERTY keyboard (except 'V', which was 96 percent). According to the firm, the ‘W’ key had the lowest hit rate, while the ‘Q’ key had the highest hit rate. The average hit rate was about 95 percent. Not surprisingly, the keys on the outside of the keyboard, such as Q, A, Z, and P, L, and M, had high hit rates.
Some of those same keys, however, were pressed more inadvertently that others. Dubbed "false alarm rates," the study found that participants were repeatedly pressing certain keys when they intended instead to press other adjacent keys ("false alarm key"). Several iPhone keys had high false alarm rates: Q (66%), P (27%), J (22%), X (21%), and Z (15%). In contrast, the median false alarm rate across the iPhone entire keyboard was just 5.48 percent.
Both iPhone and QWERTY keys with the highest false alarm rates were those in close proximity to the five most frequently used letters in the English language -- E, T, A, O, and I. In addition to the high false alarm letters listed above, other false alarm letters included 'W' (10%), 'R' (6.5%), 'Y' (8.7%), and 'S' (6.0%), which are also adjacent to high-frequency letters. The study also found that the letter 'B' (8.2%) also had a high false alarm rate, potentially because of its location near the letter N (which is the sixth most frequent letter). All keys on a QWERTY device had false alarm rates of less than 3 percent (except 'Q', which was 8%).
The firm also found that Q and P keys were problematic for users of both keyboards, suggesting that the issue for these keys arises from their location near the top edges of the keyboards.