Significant difference between the auditors expectation and the entity\'s book value require explanation through quantification, corroboration and evaluation. Explain each of these terms

Explanations for significant differences observed for substantive analytical procedures must be followed up and resolved through quantification, corroboration, and evaluation.
Quantification: Quantification involves determining whether the explanation or error can explain the observed difference. This may require the recalculation of the expectation after considering the additional information. For example, a client may offer the explanation that the inventory account increased by a certain percentage as compared to the prior year due to a 12 percent increase in raw materials prices. The auditor should compute the effects of the raw materials price increase and determine the extent to which the price increase explains (or does not explain) the increase in the inventory account.
Corroboration: Auditors must corroborate explanations for unexpected differences by obtaining sufficient competent audit evidence linking the explanation to the difference and substantiating that the information supporting the explanation is reliable. This evidence should be of the same quality as the evidence obtained to support tests of details. Common corroborating procedures include examination of supporting evidence, inquiries of independent persons, and evaluating evidence obtained from other auditing procedures.
Evaluation: Evaluation involves the effective use of professional skepticism, combined with the desire to obtain sufficient appropriate audit evidence, similar to other auditing procedures. The auditor should evaluate the results of the substantive analytical procedures to conclude whether the desired level of assurance has been achieved. If the auditor obtains evidence that a misstatement exists and can be sufficiently quantified, the auditor makes note of his or her proposed adjustment to the client's financial statements.