問48
頻出度★★★
システム開発における，エラーを検出した時期とその不具合の修正にかかる対応費用の関係を最も適切に示したグラフはどれか。
平成21年度 秋期 ITパスポート試験 問48
マネジメント系システム開発技術 › システム開発技術
This question's explanation and your answers so far.
解説
問 48
- ア
正解 Graph ア is an upward-sloping curve: as the horizontal axis moves through design, manufacturing (coding), testing, and operation, the correction cost on the vertical axis starts out rising gently and then climbs steeply near the end. If an error is found during design, fixing it means only editing wording in the design document. But if the same error is found during manufacturing, the program must be rebuilt; during testing, the tests must be run again; and during operation, it may require correcting production data, notifying users, and releasing a new version. In other words, the further the process advances, the more deliverables have been built on top of that error, so the scope of rework and the number of people involved both grow. Graph ア is the one that best expresses this relationship of the later the discovery, the more sharply the correction cost rises, which is exactly why doing reviews and tests thoroughly in the upstream stages is regarded as a basic of quality management.
Incorrectイ
This is a downward-sloping curve, highest at the design stage and decreasing toward operation, which is the opposite of reality. An error at the design stage is fixed on paper and is therefore the cheapest, while an error at the operation stage is the most expensive. The shape of イ would wrongly suggest that finding an error earlier costs you more.
Incorrectウ
This is a V-shaped curve that is lowest between the manufacturing and test stages, which implies that the design stage and the operation stage are both equally high. There is no basis for a fix at the design stage costing as much as one at the operation stage, nor any reason for the cost to dip partway through. It does not match the reality that the more upstream the stage, the cheaper the fix.
Incorrectエ
This shape keeps the cost constant from design through testing and jumps sharply in a step only at the operation stage. It is correct that the operation stage is expensive, but it fails to express the stepwise increase by which rework, and therefore cost, also grows as the process advances among the design, manufacturing, and testing stages. As the graph that most appropriately shows the relationship, it is inferior to ア.
ここがポイント
- The cost of correcting an error grows the further downstream the stage at which it is found. As work advances from design to manufacturing to testing to operation, deliverables built on top of that error pile up, so the scope of rework expands exponentially.
- Because of this property, securing quality in the upstream stages, such as through joint reviews (finding and fixing problems early), becomes a highly cost-effective means of quality management.
用語