how many ratings does a user need before a movie will be recommended why is a probe set important? how to use a probe set in netflix when creating a probe set of ratings, how many ratings should you use? why is the training set important for a recommendation algorithm how many ratings are in a probe set how to train a recommendation algorithm what is the purpose of a probe set in netflix how many ratings is a probe set how to use neural network to validate a recommendation algorithm how many ratings in a training set can you do probe sets and training sets how to use probe set how to create a probe set for training? do i overfit the training set and the probe set in a movie recommendation algorithm? how do i separate ratings into two groups how to treat rare items in the validation of a recommender system how to use a probe set for validation how to validate the recommendation algorithm of netflix how to use probe set