Daniel Voigt Godoy - Deep Learning with PyTorch Step-by-Step A Beginner’s Guide-leanpub

Equation 0.6 - Computing mean and standard deviation
Then, it uses both values to scale the feature:
Equation 0.7 - Standardizing
If we were to recompute the mean and the standard deviation of the scaled
feature, we would get 0 and 1, respectively. This pre-processing step is commonly
referred to as normalization, although, technically, it should always be referred to as
standardization.
IMPORTANT: Pre-processing steps like the StandardScaler
MUST be performed AFTER the train-validation-test split;
otherwise, you’ll be leaking information from the validation and /
or test sets to your model!
After using the training set only to fit the StandardScaler, you
should use its transform() method to apply the pre-processing
step to all datasets: training, validation, and test.
52 | Chapter 0: Visualizing Gradient Descent