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.