# Tensor Flow Time Series Tutorial Question

In the tutorial, they normalize the data and say "The mean and standard deviation should only be computed using the training data"

What does this refer to? Why should you only use the training data?

• As far as I know, tf.keras.utils.normalize does not use mean and std (nor min max scaler). It uses Lp-norms (check this question. – TitoOrt May 12 '20 at 13:07
• As with any normalization method you must feed it just the data you want it to see. If your validation_split is 0.1 then you'd use the first 90% of the data to estimate normalization parameters. – NikoNyrh May 12 '20 at 19:48