why do you use the test section and the training portion which step of the data analysis is used for cross-validation? what is cross validation in java why do we use training, validation and cross-validation why is cross validation biased when using training data? how to compare training validation and training when can you use the same data for feature selection what is meant by training and validation what is the difference between testing and training what is the difference between training and validation and cross validation? how many sample do i need to run cross validation cross validation definition when using different data for feature selection what is used for cross validation what is meant by cross validation what is the purpose of cross validation why do we use training to test the model? what is the purpose of training and validation data? is the training part of the data used for cross-validation? what is the testing portion can a classifier be tested against a training data set