Script for straightliners

Hello, everyone,

I am trying to write a Perl script to identify straighlining behavior with grid questions. In total I have three grid questions called...

ItemsIdentity
ItemsAttitudes
ItemsAttitudes2

with six, ten and six questions. Now I wanna know if a respondent always picks the same answer on a seven point Likert-scale. If he or she does, then there is zero variance in the answers.

Now, my script looks like this:

[% Begin Unverified Perl

# Exercises
my @exername = ("ItemsIdentity_r", "ItemsAttitudes_r", "ItemsAttitudes2_r");
my @exernums = (6, 10, 6);
my $nScales = scalar @exername

# Calculate the mean
my @answers = ();
my $j=1;
for (my $k = 1; $k <= $nScales; $k++) {
	for (my $i = 1; $i <= $exernums[k]; $i++) {
		$answers[j] = GETVALUE($exername[k]) . $i;
		j=j+1;
}
}

my $answers_mean = mean(@answers)

# Check for straightlining behavior
$straightliner = 0;
$sqtotal = 0;

foreach (@$answers) {
	$sqtotal += ($_ - $answers_mean) ** 2
}

if ( $sqtotal==0 ) {
	$straightliner = 1;
}

SET("SetStraightliner_Dummy",$straightliner);

End Unverified %]