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No, you cannot conclude that. You have not seen the GPA/LSAT scores of those applicants. Furthermore, Duke has higher grade inflation. According to gradeinflation.com, the difference is 3.40 vs 3.44 in 2007. That doesn’t sound like much but note that the number for NU includes those in specialty schools that have more grade inflation (3.5+). The average GPA for college of arts&sci, where most prelaws are, is less than that (last I saw the actual data by school from Daily Northwestern, I remember it was 3.25 for arts & sci and 3.21 for engineering while specialty schools have something like 3.5+). Now, 3.25 vs 3.44 is quite a difference! While some specialty schools students can be law school applicants, their majors are usually viewed less favorably by elite law schools; this got nothing to do with Duke vs Northwestern, more like english/poli sc/history vs communication/education/journalism majors.</p>
<p>Perhaps Duke is just an easier school. 
Nothing wrong with that and in fact, I wish they make NU a bit easier. They should make the orgo average as a B like other peers, instead of B-/C+. The President mentioned a plan to decrease the number of courses for requirement (48 for engineering and 45 for others). I hope the plan is still alive.</p>