An appraiser encounters an underground storage tank and there are no signs of leakage or failure. An appraisal could be performed under the presumption that the tank is not leaking and the property is not contaminated. This would be an example of a(n) .

Extraordinary assumption

Explanation: Appraisal could be defined as the estimation or evaluation of an object, property or structure in other to determine either the worth, condition or nature of such property or object.

An Extraordinary assumption during appraisal means a presumption that certain unknown information exists or is a fact. It assumes a condition which is unknown to be true and as such if the information is found to be false may alter the result or conclusion of the appraisal.

Such is the scenario above, when the appariser assumes there is no leakage or contamination based merely on unknown fact.

what terms are there?