ABXTEST(1) MPEG Audio Decoder ABXTEST(1)NAMEabxtest - double-blind ABX comparison testing script
SYNOPSISabxtest [-n min] [-m max] [-g goal] A-cmd B-cmd
DESCRIPTIONabxtest is a tool for conducting listening (or other subjective) tests
to determine whether a listener can discern a difference between two
subjects under test, denoted A and B.
The listener conducts several trials in which an unknown subject, X, is
randomly chosen to be either A or B. The probability that X is A or B
is the same. The listener must decide whether X sounds the same as A or
the same as B. The listener may repeat A, B, and X as many times as
necessary before reaching a verdict.
In order to prove the hypothesis that a difference can be discerned
between A and B, the listener must disprove the null hypothesis that A
sounds the same as B. This is accomplished by correctly identifying X
often enough that randomly guessing correctly the same number of times
would be statistically improbable.
The A and B subjects for abxtest are actually arbitrary shell commands.
The normal mode of use would be to give commands which play two
slightly different sounds. The standard output and standard error from
each command are suppressed so as not to reveal the identity of X. The
listener may interrupt an executing command (usually by pressing ^C)
without terminating the test.
OPTIONS-n min Set the minimum number of trials. Trials will continue after
this number if the statistical probability goal has not yet been
met. The default is 10.
-m max Set the maximum number of trials. Trials will end after this
number even if the statistical probability goal has not been
met. The default is 20.
-g goal
Set the minimum statistical probability goal. This is the proba‐
bility that the number of correct identifications is the same as
random guesses. In order to disprove the null hypothesis, the
result of the test must be a probability less than or equal to
this goal. The default is 0.05.
FILES
/dev/random
By default this file is read to generate a random sequence of X.
ENVIRONMENT
RANDOM_FILE
If set, the file named by this variable will be read instead of
/dev/random to generate a sequence of X.
NOTESabxtest uses the binomial distribution to accurately calculate the
probability that the result is the same as random guesses.
AUTHOR
Robert Leslie <rob@mars.org>
MAD 16 November 2000 ABXTEST(1)