This document provides a review of published methods that have been used to provide estimates of the levels of distortion and/or the concomitant loss of stability pressure ratio that can occur when the recommended full complement of aerodynamic interface plane high-response instrumentation is not used when obtaining inlet data. The methods have been categorized based on the underlying mathematical representation of the aerophysics. Further, the use of maximum value statistics, which has been used to further improve the results where short-duration time records have been employed, is discussed.