Lehrstuhl Mathematik & InformatikGeneral Bounds on the Number of Examples Needed for Learning Probabilistic Concepts
Abstract. Given a p-concept class C, we define two important functions dC(gamma), d'C(gamma) (related to the notion of gamma-shattering). We prove a lower bound of Omega((dC(gamma)-1)/(epsilon(gamma)2)) on the number of examples required for learning C with an (epsilon, gamma)-good model of probability. We prove similar lower bounds for some other learning models like learning with gamma-bounded absolute (or quadratic) difference or learning with a gamma-good decision rule. For the class ND of nondecreasing p-concepts on the real domain, dND(gamma)=Omega(1/gamma). It can be shown that the resulting lower bounds for learning ND (within the models in consideration) are tight to within a logarithmic factor. In order to get the "almost-matching" upper bounds, we introduce a new method for designing learning algorithms: dynamic partitioning of the domain by use of splitting trees. The paper also contains a discussion of the gaps between the general lower bounds and the corresponding general upper bounds. It can be shown that, under very mild conditions, these gaps are quite narrow.