Guess what letter iPhone texters trip up on the most

It's this letter [at left]. But read on for the details about how this assertion was proved.
Written by Russell Shaw, Contributor

It's this letter [at left]. But read on for the details about how this assertion was proved.

Chicago-based usability consultancy UserCentric is out with a new report that says iPhone users make more errors during texting than these same people do on traditional QWERTY-handsets.

Not only were a total of 60 users tested for errors, but the tests were so exacting they even drilled down toward accuracy in tapping out individual letters of the alphabet.

First, here's how UserCentric described the methodology used:

Our study involved data from 60 participants who were asked to enter specific text messages and complete several mobile device tasks. Twenty of these participants were iPhone owners who owned their phones for at least one month. Twenty more participants were owners of traditional hard-key QWERTY phones and another twenty were owners of numeric phones who used the “multi-tap” method of text entry.

Participants were brought in for 75 minute one-on-one usability sessions with a moderator. Each participant entered six fixed-length text messages on their own phone. Non-iPhone owners also did six messages each on the iPhone and a phone of the “opposite” type. The opposite phone for numeric phone owners was a Blackberry and for hard-key QWERTY phone owners it was a numeric Samsung E300 phone. Some participants did additional tasks, including a contact search and add contacts, as time allowed.

OK, fair enough. Now let us go to a more specific description of the testing, and what was found:

iPhone owners entered six text messages on their own phone. They also typed two pangrams – a sentence that includes every letter in the English language at least once – and one corpus – a set of characters that represents the exact letter frequencies of the English language. These tasks were included to ensure that participants experienced the various phone keyboards in a thorough manner. iPhone owners also completed tasks involving text correction, contacts, and visual voicemail

Non-iPhone owners entered a total of 18 text messages – six each on their own phone (hard-key QWERTY or numeric phone), the iPhone, and the “opposite” phone (numeric test phone for QWERTY phone owners, hard-key QWERTY test phone for numeric owners). These participants also entered two pangrams and one corpus on their own phone and completed the contact list tasks if time was remaining.

I won't go into the arcane scoring system. Instead I will spare your brain by getting straight to the details as described by UserCentric:

iPhone and Hard-Key QWERTY Texting Was Equally Rapid, but iPhone Owners Made More Errors

When compared to hard-key QWERTY phone owners using their personal phones, iPhone owners’ rate of text entry on the iPhone was equally rapid. However, iPhone owners made more errors during text entry and also left significantly more errors in the completed messages.

While iPhone owners made an average of 5.6 errors/message on their own phone, hard-key QWERTY owners made an average of 2.1 errors/message on their own phone, p < .01. iPhone owners also left an average of 2.6 errors/completed message created on the iPhone compared to an average of 0.8 errors/completed message left by hard-key QWERTY phone owners on their own phone.

“Despite the correction features available on the iPhone, this data suggests that people who have owned it for a month are still making about the same number of errors as the day they got it,” says Gavin Lew, Managing Director.

Furthermore, when iPhone owners were asked to perform a text correction task during their sessions, 21% of iPhone owners were not aware of the magnifying glass correction feature although they had owned their iPhone for one month. Participants who did know about the feature clearly loved it, and participants who were new to it indicated that it would be useful in the future.

A matrix was constructed using data from about 34 participants using the iPhone, both owners and non-owners. The matrix allowed us to compare the letters that participants intended to enter (based on the task) with the actual letters entered. Afterwards, we identified hits, misses, false alarms, and correct rejections for each letter on the iPhone keyboard.

In general, hit rates for all keys on the iPhone keyboard were consistently 90% or higher. Hit rate refers to the percentage of time that a key was correctly pressed when it was intended. The ‘W’ key had the lowest hit rate, while the ‘Q’ key had the highest hit rate. The average hit rate was about 95%. To generalize, the keys on the outside of the keyboard, such as Q, A,, Z, and P, L, and M, had high hit rates.

However, the false alarm rates indicated that participants were repeatedly pressing certain keys when they intended instead to press other adjacent keys. For example, a false alarm for a given letter is said to have occurred if a participant meant to press ‘W’ and instead pressed ‘Q’. This would count as a miss for ‘W’ and a false alarm for ‘Q’. False alarms are relevant because they increase the time used to enter and correct a text message.

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 5.48%.

iPhone 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. 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).

Participants made different types of errors on the iPhone and the hard-key QWERTY phones. The majority of errors made on the iPhone involved substituting a nearby letter for the intended letter. However, on the QWERTY phone, participants made more insertion and omission errors than substitution errors. Also, many of the substitution errors that were made on the QWERTY keyboards involved swapping the order of the correct letters in the words, such as typing “stomr” instead of “storm”.

As a result, UserCentric concludes the iPhone May Not be Suitable for Heavy Text Use:

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 iPhone was clearly associated with higher text entry error rates than a hard-key QWERTY phone. The finding that iPhone owners made more texting errors on iPhones than their hard-key QWERTY counterparts (on their own QWERTY phones) suggests that the iPhone may have a higher fundamental error rate. Specifically, the high rate of false alarms for iPhone keys adjacent to high frequency letters is troubling. 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.

“The 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,” recommended Lew.

OK, let us all practice. Q. Q.Q.

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