Quality costs can also be classified as observable or hidden. Observable quality costs
are those that are available from an organization’s accounting records. Hidden quality costs
are opportunity costs resulting from poor quality. (Opportunity costs are not usually recognized
in accounting records.) Consider, for example, all the examples of quality costs listed in the prior
section. With the exception of lost sales, customer dissatisfaction, and lost market share, all the
quality costs are observable and should be available from the accounting records. Note also
that the hidden costs are all in the external failure category. These hidden quality costs can be
significant and should be estimated. Although estimating hidden quality costs is not easy, three
methods have been suggested: (1) the multiplier method, (2) the marker research method, and
(3) the Taguchi quality loss function.