1.4 Quality Cost

Product quality costs can be classified into:

The costs of control (prevention costs, appraisal costs) combined with,

The costs of failure (internal failure costs, external failure costs).

Costs of control

		Include costs that are spent to prevent and detect software errors in order to reduce them to an accepted
		level.

		Prevention costs include investments in quality infrastructure and quality activities that are not directed to a
		specific project or system, being general to the organization.

		Appraisal costs include the costs of activities performed for a specific project or software system for the
		purpose of detecting software errors. They are devoted to detection of software errors.

Costs of failure

		Costs of failure of control include costs of failures that occurred because of failure to prevent and detect
		software errors.

1.4 Quality Cost

		Internal failure costs include costs of correcting errors that have been detected by design reviews, software
		tests and acceptance tests (carried out by the customer) and completed before the software is installed at
		customer sites.

		External failure costs include all costs of correcting failures detected by customers or the maintenance team
		after the software system has been installed.