<?php
function
mean(
$arr
,
$n
)
{
$sum
= 0;
for
(
$i
= 0;
$i
<
$n
;
$i
++)
$sum
=
$sum
+
$arr
[
$i
];
$mean
= (float)(
$sum
/
$n
);
return
$mean
;
}
function
sd(
$arr
,
$n
)
{
$sum
= 0;
for
(
$i
= 0;
$i
<
$n
;
$i
++)
$sum
=
$sum
+ (
$arr
[
$i
] - mean(
$arr
,
$n
)) *
(
$arr
[
$i
] - mean(
$arr
,
$n
));
$sdd
=
$sum
/
$n
;
return
$sdd
;
}
function
combinedVariance(
$arr1
,
$arr2
,
$n
,
$m
)
{
$mean1
= mean(
$arr1
,
$n
);
$mean2
= mean(
$arr2
,
$m
);
echo
(
"Mean1: "
.
round
(
$mean1
, 2) .
" "
.
" mean2: "
.
round
(
$mean2
, 2));
$sd1
= sd(
$arr1
,
$n
);
$sd2
= sd(
$arr2
,
$m
);
echo
(
"\nStandardDeviation1: "
.
round
(
$sd1
, 2) .
" "
.
" StandardDeviation2: "
.
round
(
$sd2
, 2));
$combinedMean
= (float)(
$n
*
$mean1
+
$m
*
$mean2
) / (
$n
+
$m
);
echo
(
"\nCombined Mean: "
.
round
(
$combinedMean
, 2));
$d1_square
= (
$mean1
-
$combinedMean
) *
(
$mean1
-
$combinedMean
);
$d2_square
= (
$mean2
-
$combinedMean
) *
(
$mean2
-
$combinedMean
);
echo
(
"\nd1 square: "
.
round
(
$d1_square
, 2) .
" "
.
" d2_square: "
.
round
(
$d2_square
, 2));
$combinedVar
= (
$n
* (
$sd1
+
$d1_square
) +
$m
* (
$sd2
+
$d2_square
)) /
(
$n
+
$m
);
return
$combinedVar
;
}
$arr1
=
array
( 23, 45, 34,
78, 12, 76, 34 );
$arr2
=
array
( 65, 67, 34, 23, 45 );
$n
= sizeof(
$arr1
);
$m
= sizeof(
$arr2
);
echo
(
"\nCombined Variance: "
.
round
(combinedVariance(
$arr1
,
$arr2
,
$n
,
$m
), 2));
?>