Design and Analysis. The study was a within-subjects
factorial design with two factors, Method and Order. The
levels of Method were (PassChords, VoiceOverPIN) and the
levels of Order were (1, 2). The Order factor indicated
whether the current Method was performed first or second in
the study, allowing us to evaluate possible crossover effects.
We analyzed two measures: authentication time and failure
rate. The former was measured as the difference between
the time of the first and last touch events of a password (including
PassChord calibration), and the flatter was the proportion
of times the user failed to authenticate. The failure
rate included completed passwords that turned out to be incorrect,
not counting errors that were corrected by the user
with the backspace key or a re-calibration. Such errors
were subsumed by the password entry time. Both measures
were analyzed with mixed-effects model analysis of variance,
with a fixed effect for Method and a random effect for Participant
to account for correlated measurements for different
methods within subjects. Authentication times were averaged
for trials in each method. We used a significance level
of α = 0.05