use List::Util qw( sum );

my %data;
while (<>) {
    chomp;
    my ($k, $v) = split /\t/;
    push @{ $data{$k} }, $v;
}

local $, = "\t";
local $\ = "\n";
for my $k (keys %data) {
    my $data = $data{$k};
    print $k, 0+@$data, sum(@$data)/@$data;
}