A multi layer reservoir may have a pressure behavior different from that of a single layer reservoir, and objective of well test analysis is to obtain individual layer permeability and skin factors.

The integrand includes a multiplying factor of the vertical directivity of the noise intensity, and the layered ocean environment affects the spatial coherences via this directivity factor.

The main approach to solve this problem is to stratify the population studied through taking the confounder as the stratifying variable.