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#! /bin/sh
#
# abxtest - simple ABX double-blind testing script
# Copyright (C) 2000-2004 Robert Leslie
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
# $Id: abxtest,v 1.18 2004/02/23 21:34:53 rob Exp $
#
min=10
max=20
goal=.05
version="0.15.2 (beta)"
publishyear="2000-2004"
author="Robert Leslie"
usage() {
echo >&2 "Usage: $0 [-n min] [-m max] [-g goal] A-cmd B-cmd"
exit $1
}
banner() {
echo >&2 \
"ABX Double-Blind Test $version - Copyright (C) $publishyear $author"
}
while [ $# -gt 0 ]
do
case "$1" in
--help)
usage 0
;;
--version)
banner
exit 0
;;
-n)
test $# -gt 1 || usage 1
min="$2"
shift 2
;;
-m)
test $# -gt 1 || usage 1
max="$2"
shift 2
;;
-g)
test $# -gt 1 || usage 1
goal="$2"
shift 2
;;
--)
shift
break
;;
-*)
usage 1
;;
*)
break
;;
esac
done
test $# -eq 2 || usage 1
banner
echo "minimum $min, maximum $max trials"
echo "statistical goal to disprove null hypothesis is p <= $goal"
A="$1"
B="$2"
echo "randomizing ..."
tmp="/tmp/abx.$$"
trap "rm -f $tmp" 0
rand="${RANDOM_FILE:-/dev/random}"
od -t o1 -N "$max" "$rand" >$tmp || exit 2
exec 3<$tmp
actual=""
trial=1
while read <&3 line
do
set -- $line
shift
while [ $# -gt 0 ]
do
case $1 in
*[0246]) x="A" ;;
*[1357]) x="B" ;;
*)
echo >&2 "bad output from od"
exit 3
;;
esac
shift
eval x$trial=$x
actual="$actual$x"
trial=`expr $trial + 1`
done
done
exec 3<&-
rm -f $tmp
probability() {
bc <<EOF
define f(x) {
auto i;
if (x == 0) return (1);
i = x;
while (--i > 1) x *= i;
return (x);
}
define c(n, r) {
return (f(n) / (f(n - r) * f(r)));
}
define p(r, n, p) {
return (c(n, r) * (p ^ r) * ((1 - p) ^ (n - r)));
}
define g(r, n) {
auto p;
while (r <= n) p += p(r++, n, 0.5);
return (p);
}
scale = 7;
g($1, $2)
EOF
}
notdisproved() {
return `bc <<EOF
if ($1 <= $2) 1
if ($1 > $2) 0
EOF`
}
if (echo "testing\c"; echo 1,2,3) | grep c >/dev/null
then
if (echo -n testing; echo 1,2,3) | sed s/-n/xn/ | grep xn >/dev/null
then
n="" c='
'
else
n="-n" c=""
fi
else
n="" c='\c'
fi
input=""
votes=""
trials=0
correct=0
prob=1
echo
trial=1
while [ $trial -le "$min" ] || {
[ $trial -le "$max" ] && notdisproved $prob $goal
}
do
echo $n "trial $trial: $c"
X=`eval eval echo \\\\\$\\\$x$trial`
if [ -z "$input" ]
then
echo "play [a] / play [b] / play [x] / vote [A] / vote [B] / [stop]"
echo $n "> $c"
if read input
then
continue
else
break
fi
fi
case "$input" in
a|b|x)
input=`echo $input | tr abx ABX`
echo "playing $input ..."
cmd=`eval echo \\\$$input`
trap "" 2
sh -c "$cmd" 1>/dev/null 2>$tmp
status=$?
if [ $status -eq 0 -o $status -ge 128 ]
then
rm -f $tmp
trap - 2
else
cat >&2 $tmp
exit $status
fi
input=""
;;
A|B)
echo "voting for $input"
eval vote$trial="$input"
votes="$votes$input"
if [ $input = "`eval echo \\\$x$trial`" ]
then
correct=`expr $correct + 1`
fi
trials=$trial
prob=`probability $correct $trials`
trial=`expr $trial + 1`
input="x"
;;
stop)
echo "stopping"
break
;;
*)
echo "invalid input"
input=""
;;
esac
done
echo
echo "$trials trials completed"
echo "A = $A"
echo "B = $B"
echo
echo " votes: $votes"
echo " actual: $actual"
echo $n "correct: $correct/$trials$c"
if [ $trials -gt 0 ]
then
echo $n " (`expr \( $correct \* 1000 / $trials + 5 \) / 10`%)$c"
fi
echo
echo
echo "probability (p) of result being the same as random guesses = $prob"
if notdisproved $prob $goal
then
echo "failed to disprove null hypothesis (p > $goal)"
exit 9
else
echo "null hypothesis disproved (p <= $goal)"
exit 0
fi
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