QUESTION 9

A -When we have a small amount of training data, which method shall we use to validate the model?

		Training and validating on the full set of training data
		Holding back 20% of the data from the training of the model, and use this holdout set to check the model performance
		Use cross-validation by training several machine learning models on subsets of the available training data and evaluating them on the complementary subset of the data
		Use the testing dataset to validate the model

B-What can model validation be used for?

1. 		Choose the right class of model
   		Choose the best model hyperparameters
   		Estimate the performance of a given model and hyperparameter setting
   		Choose the right subset of data for training the model