To improve the performance of statistical learning methods for predictive maintenance, you need to follow a systematic and iterative process that involves data preparation, model selection, model training, model validation, and model deployment. When preparing the data, tasks such as handling missing values, normalizing, encoding categorical variables, creating features, reducing dimensionality, balancing or resampling the data, and splitting it into training, validation, and test sets can help. For model selection, consider the type and size of the data, complexity of the system, interpretability of the model, accuracy and computational cost of the model, and availability and quality of documentation and support. Model training can be done with grid search, random search, Bayesian optimization or cross-validation. Model validation should be done on a new and unseen data set to assess how well it generalizes to new situations or how robust it is to noise or uncertainty. Hold-out validation, bootstrap validation or time-series validation are some methods that can help. Finally for model deployment consider steps such as model packaging, testing, monitoring and updating. This will help you achieve desired outcomes from predictive maintenance such as cost reduction or safety improvement.