A sorority did not owe a duty of care to guests of its off-campus party to protect them from assault and battery by uninvited persons crashing the party. The measures that plaintiff claimed the sorority should have taken to prevent the harm–hiring private security personnel and maintaining and enforcing an invited guest list–were highly burdensome. To justify that degree of burden, plaintiff would have to show that harm was also highly foreseeable, but he could not do so. Mere knowledge of crimes committed at fraternity parties at the same campus was insufficient. Also, the sorority assumed no greater duty of care to guests by agreeing to the campus’ guidelines for off-campus parties. The sorority did not increase the risk of harm by agreeing to those guidelines, and plaintiff didn’t rely on that agreement in deciding to go to the party.