Erlingsson et al give a poetic description of privacy-preserving analysis in their RAPPOR paper . They say that the goal is to
… allow the forest of client data to be studied, without permitting the possibility of looking at individual trees.
 Úlfar Erlingsson, Vasyl Pihur, and Alexsandra Korolova. RAPPOR: Randomized Aggregatable Privacy-Preserving Ordinal Response. Available here.