When building statistical or machine learning prediction models—such as Linear Regression, Logistic Regression, or Random Forest—within the Analytics view, the “Test Data” column in the Predictions on Training Data section indicates whether a specific row is designated as test data.
By default, Exploratory uses all data as training data (data for building the model). Therefore, the value for all rows will be FALSE under the default settings.
However, if you enable Test Mode in the Analytics properties, the data is split into training and test sets. In this case, rows assigned to the test set will show TRUE.
For more details on model testing (evaluating model performance), please refer to the following link: