 These subjects have the greatest disparity between their actual performance (at the low end of the distribution) and their self-rating (placing themselves above average).
<clarity>  These subjects have the greatest disparity between their actual performance (at the low end of the distribution) and their self-rating (placing themselves above average).
 These subjects have the greatest disparity between their actual performance (at the low end of the distribution) and their self-ratings (placing themselves above average).