With the intent to detect inappropriate response patterns, the lz index (Drasgow, Levine & Williams, 1985) was applied to a 64-item test of second language reading ability administered to 171 university students. Our goal was to compare intuitive rejection of research data to data elimination suggested by lz. In addition, lz was challenged to detect 12 additional participants who had responded by pseudo-chance. Results suggest that although lz detects efficiently aberrant response patterns for large groups and that it proves superior to intuitive rejection, that index has limitations when it comes to analyzing smaller data matrices.