ISTQB-ATM practice question 10 of 15

Assume you have some data related to confirmation testing during system testing of a past project. In that project 240 bug reports have been opened…

Assume you have some data related to confirmation testing during system testing of a past project. In that project 240 bug reports have been opened once, 80 were opened twice, 10 were opened three times and no bug reports have been opened more than three times. You estimate that a bug report, which has failed its confirmation test, costs, on average, 3 personhours. Which of the following statements correctly describe the value of these confirmatory testing activities based on cost of quality? K3 2 credits

Answer options

A: 300 person-hours have been spent on the project during the system testing phase, because of the failed confirmation tests and this cost belongs to the costs of internal failure Correct answer

B: 340 person-hours have been spent on the project during the system testing phase, because of the failed confirmation tests and this cost belongs to the costs of external failure

C: 340 person-hours have been spent on the project during the system testing phase, because of the failed confirmation tests and this cost belongs to the costs of internal failure

D: 300 person-hours have been spent on the project during the system testing phase, because of the failed confirmation tests and this cost belongs to the costs of detection

Correct Answer:

A. 300 person-hours have been spent on the project during the system testing phase, because of the failed confirmation tests and this cost belongs to the costs of internal failure

Explanation

The total cost is calculated from the number of failed confirmation tests. Bugs opened twice failed confirmation testing once (80 bugs 1 failure = 80 failures). Bugs opened three times failed confirmation testing twice (10 bugs 2 failures = 20 failures). The total number of failures is 80 + 20 = 100. The total cost is 100 failures 3 person-hours/failure = 300 person-hours. According to the Cost of Quality model, costs associated with defects found and fixed before delivery to the customer are classified as internal failure costs. This includes the cost of re-work and re-testing, which is precisely what a failed confirmation test entails.

Why Incorrect

B. The cost calculation is incorrect. Also, since the failures occurred during system testing (pre-release), they are internal, not external, failures.
C. The cost calculation is incorrect. While it correctly identifies the cost type, the value of 340 person-hours is wrong.
D. This cost is misclassified. Detection (or appraisal) costs are for the initial act of finding defects, not the cost of re-work after a failed fix.

References

1. ISTQB Advanced Level Test Manager Syllabus v3.1.2 (2023), Section 3.2.2, "Cost of Quality". This section defines internal failure costs as "Costs associated with defects found before the software is released to the customer," and explicitly lists "Re-work (e.g., fixing the defects), re-testing, regression testing" as examples. This directly supports classifying the cost of failed confirmation tests as an internal failure cost.

2. Mays, R. G. (1990). Measuring the Cost of Quality in Software Development (Technical Report CMU/SEI-90-TR-026). Carnegie Mellon University, Software Engineering Institute. Section 2.1, "Failure Costs," defines internal failure costs as "the costs of correcting problems before product delivery." It includes "rework, repair, and retest" as primary components of this category, which aligns with the scenario in the question. (Available at: https://resources.sei.cmu.edu/library/asset-view.cfm?assetid=11371)

3. Pressman, R. S., & Maxim, B. R. (2020). Software Engineering: A Practitioner's Approach (9th ed.). McGraw-Hill. Chapter 17, "Software Quality Assurance," discusses the Cost of Quality. It defines internal failure costs as those incurred when an error is detected in a product prior to shipment, including the costs of rework and failure analysis. This standard textbook corroborates the classification used in the correct answer.

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