You aren't clearing $sum at the beginning of each outer loop. Try this:

#!/usr/bin/perl
use strict;
use warnings;

my $sampleSize = 7;
my ($sum, $ssum);
for my $i (1..1000){
    $sum = 0;
    for my $j (1..$sampleSize){
        $sum+=rand();
    }
    $sum/=$sampleSize;
    $ssum+=$sum;
}
$ssum/=1000;
print "$ssum\n";

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If you think you've found a show-stopping bug in a core function that others have been using successfully for years or decades, it's a good idea to examine your own code before declaring it a bug in Perl.

Edited to add: Besides, how could the rand() function "know" how many times you're about to call it, or how many you're not going to call it? Short of a maliciously buggy dev-teasing version of Perl, which is too far-fetched to consider, there's no possible mechanism that could do this.

In reply to Re: Perl rand() generates larger numbers for small sample size, bug! by Bethany
in thread Perl rand() generates larger numbers for small sample size, bug! by ravipatel4

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