Why Three consecutive batches taken for Validation

Consecutive meaning following closely with no gap or following one after another without interruption.

• The number of batches to be taken under validation depends upon the risk involved in the manufacturing Critical process parameters & critical Quality Attribute so  depends upon that manufacturer have to choose the number of batches to be validated.
• If we will consider less than two batches then the data will not be sufficient for evaluation of and to prove reproducibility of data  between batch to batch variation & if we consider more than three batches it can increase the time & cost of manufacturer which usually not preferred.
• Generally if we will require quality in the First batch, then it is accidental (co-incidental), Second batch quality is regular & third batch quality is Validation or Confirmation.

Statistical evaluation cannot be done by considering two points, because two points always draw a straight line so minimum three points required for comparison of data.