Synonym: Cross-Validation = Blind Testing
A specific technique for estimating how accurately a the given model is capable to predict the dataset Source Dataset.
It assumes that Source Dataset is split into two subsets: Training dataset and Validation dataset.
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In order to assess predictability of the model it should bee validated on the data outside the Training dataset, which is called Validation dataset.
If the If model discrepancy on Validation dataset is close to the to model discrepancy on Training dataset one can say that a given model has a good predictability within the Source Dataset range.
If model discrepancy on Validation dataset is not close to model discrepancy on Training dataset then this phenomenon is called overtraining and means that a given model realization has "remembered" the Training dataset but can not accurately predict on the data points outside the Training dataset.
Splitting the Source Dataset into Training dataset and Validation dataset can be done in different ways.
It can be done manually or randomly (see Bootstrapping).
It should be noted though that Source Dataset may not hold enough of representative events/occurrences to provide the opportunity for Cross-Validation and in this case the Goodness of fit over the Training dataset (which is the whole Source Dataset in this case) will be the only one available, thus increasing the risk of future Model Prediction.
See also
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Natural Science / System / Model / Model Validation
Formal science / Mathematics / Statistics
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