Ok I figured this out. The ratings score is stored as a custom field so I created and if statements to check whether the score was less, equal, or greater than 0 and then I can show something accordingly. Here’s how I set it up.
<?php
$ratings_score = get_post_meta($post->ID,'ratings_score',true);
if ($ratings_score < 0 ) {
echo '<span>Plus</span>';
} elseif ($ratings_score > 0 ) {
echo '<span>Minus</span>';
} else {
echo '<span>Even</span>';
}
?>