ITPEC FE Morning October 2023 Question 52
In order to determine the quality condition in a test process, it is necessary to analyze and evaluate the relationship between the number of completed test items and the cumulative number of bugs. Which of the following is a graph that indicates that the quality is becoming stable?
Explanation
Graph (d), the S-curve that flattens into a plateau — when new bugs stop turning up as more tests are completed, quality is converging.
A cumulative count can only stay level or rise, and its slope is the rate at which bugs are being found. In a typical test phase the slope is small at first (easy tests, testers ramping up), steep in the middle (most defects found) and then close to zero. The flat tail of graph (d) means additional test items find almost no new bugs, which is the sign of stable quality. This is the reliability growth (Gompertz or logistic) curve.
Answer (d)
Why not others:
- •(a) — the curve falls, which a cumulative count cannot do
- •(b) — the slope keeps increasing, so bugs are being found faster and faster; quality is getting worse, not stabilising
- •(c) — a straight line means bugs appear at a constant rate with no sign of convergence
Key rule: On a cumulative bug curve, read the slope: quality stabilises only when the slope approaches zero and the curve saturates.
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