1ABXTEST(1) MPEG Audio Decoder ABXTEST(1)
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6 abxtest - double-blind ABX comparison testing script
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9 abxtest [-n min] [-m max] [-g goal] A-cmd B-cmd
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12 abxtest is a tool for conducting listening (or other subjective) tests
13 to determine whether a listener can discern a difference between two
14 subjects under test, denoted A and B.
15 The listener conducts several trials in which an unknown subject, X, is
17 randomly chosen to be either A or B. The probability that X is A or B
18 is the same. The listener must decide whether X sounds the same as A or
19 the same as B. The listener may repeat A, B, and X as many times as
20 necessary before reaching a verdict.
21 In order to prove the hypothesis that a difference can be discerned
23 between A and B, the listener must disprove the null hypothesis that A
24 sounds the same as B. This is accomplished by correctly identifying X
25 often enough that randomly guessing correctly the same number of times
26 would be statistically improbable.
27 The A and B subjects for abxtest are actually arbitrary shell commands.
29 The normal mode of use would be to give commands which play two
30 slightly different sounds. The standard output and standard error from
31 each command are suppressed so as not to reveal the identity of X. The
32 listener may interrupt an executing command (usually by pressing ^C)
33 without terminating the test.
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36 -n min Set the minimum number of trials. Trials will continue after
37 this number if the statistical probability goal has not yet been
38 met. The default is 10.
39 -m max Set the maximum number of trials. Trials will end after this
41 number even if the statistical probability goal has not been
42 met. The default is 20.
43 -g goal
45 Set the minimum statistical probability goal. This is the proba‐
46 bility that the number of correct identifications is the same as
47 random guesses. In order to disprove the null hypothesis, the
48 result of the test must be a probability less than or equal to
49 this goal. The default is 0.05.
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52 /dev/random
53 By default this file is read to generate a random sequence of X.
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56 RANDOM_FILE
57 If set, the file named by this variable will be read instead of
58 /dev/random to generate a sequence of X.
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61 abxtest uses the binomial distribution to accurately calculate the
62 probability that the result is the same as random guesses.
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65 Robert Leslie <rob@mars.org>
66MAD 16 November 2000 ABXTEST(1)