KSPC Data
Keystrokes-per-character (KSPC) is the average number of keystrokes required to enter a single character [1]. Though ambiguous keypads allow the user to press a key once for each letter, each key press represents one of numerous (typically three) letters, thus creating ambiguity. A corpus of the target language (i.e., the word-frequency file) is used to map key sequences to actual words, but sometimes, a collision occurs (i.e., a key sequence maps to multiple words). Consequently, the candidate words are presented to the user in decreasing order of probability. The supplemental presses of the "NEXT" key, required to select the intended word from the candidate list, results in KSPC values greater than one. The KSPC26 value represents usage of only the 26 letters of the English alphabet, while the more practical KSPC27 also includes usage of the space character.
Mobile text entry poses a dilemma: large keypads provide desktop convenience, but mobile devices favour a small form factor. Ambiguous keypads alleviate this, but the mapping of characters to keys is significant. The key-character mapping efficiency (KCME) value represents a technique's balance of functionality and compactness with respect to the benchmark QWERTY layout. Values greater than 1.0 represent techniques that are more efficient than the benchmark, and values less than 1.0 represent those that are less efficient.
WPM Data
The words-per-minute (WPM) performance prediction is based on a Fitts' Law model [2]. In addition to the prediction, the panel itemizes characteristics, such as the estimated time to enter all the words in the word-frequency file (tCorpus), the number of characters necessary for such a task (nCorpus), and the average time to enter each character (tChar). The panel also displays thumb usage statistics: use of the left thumb (L), right thumb (R), sequential use of each thumb (LL, RR), and transitions from one thumb to the other (LR, RL). It also lists the number of words in the corpus that begin with keystrokes involving each thumb, and those that end with keystrokes involving each thumb.
Ambiguous Sets
Each entry in this list represents a set of words that map to the same key sequence. Consequently, entering a word in the list might require supplemental input (i.e., one or more presses of the "NEXT" key).
Keystroke Data
Each entry in this list represents a word in the corpus, its frequency in the corpus, and its associated keystrokes. The keystrokes are all terminated with a SPACE character and include all required presses of the "NEXT" key.
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