'Balance' is a term used in Re:infer to describe how well the training data for a model represents the dataset as a whole.
When Re:infer assesses how balanced a model is, it's essentially looking for labelling bias that can cause an imbalance between the training data and the dataset as a whole.
To do this, it uses a labelling bias model that compares the reviewed and unreviewed data to ensure that the labelled data is representative of the whole dataset. If the data is not representative, model performance measures can be misleading and potentially unreliable.
Labelling bias in Re:infer is typically the result of an imbalance of the training modes used to assign labels, particularly if too much 'text search' is used and not enough 'Shuffle'.
The 'Rebalance' training mode shows verbatims that are under-represented in the reviewed set. Labelling examples in this mode will help to quickly address any imbalances in the dataset.