I'll stand by my view ... I don't think it likely that 100 Harvard students (or Yale students, or Rutgers students) out of a sample of 280 would all cheat at the same time, on an open book take home exam, in a gut course, when there was absolutely no need to cheat. Not looking to excuse bad behavior, but under these facts those numbers point more to a misunderstanding or mistake (more so than the assumption that all 100 "took the easy way out" on what was already an easy exam).