Sample complexity: Difference between revisions

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In others words, the sample complexity <math>N(\rho,\epsilon,\delta)</math> defines the rate of consistency of the algorithm: given a desired accuracy <math>\epsilon</math> and confidence <math>\delta</math>, one needs to sample <math>N(\rho,\epsilon,\delta)</math> data points to guarantee that the risk of the output function is within <math>\epsilon</math> of the best possible, with probability at least <math>1 - \delta</math> .<ref name="Rosasco">{{citation |last = Rosasco | first = Lorenzo | title = Consistency, Learnability, and Regularization | series = Lecture Notes for MIT Course 9.520. | year = 2014 }}</ref>

In [[Probably approximately correct learning|probabilisticallyprobably approximately correct (PAC) learning]], one is concerned with whether the sample complexity is ''polynomial'', that is, whether <math>N(\rho,\epsilon,\delta)</math> is bounded by a polynomial in 1/''ε'' and 1/''δ''. If <math>N(\rho,\epsilon,\delta)</math> is polynomial for some learning algorithm, then one says that the hypothesis space

<math> \mathcal H </math> is '''PAC-learnable'''. Note that this is a stronger notion than being learnable.