問44
頻出度★★★
要件定義後の外部設計, 内部設計, プログラミング, 結合テスト, システムテストを行う開発プロジェクトにおいて, 生産性を規模÷工数で表すものとする。プログラミングの生産性を1とした場合の内部設計と結合テストの生産性は2, 外部設計とシステムテストの生産性は4である。外部設計に1人月を要するとき, プロジェクト全体の工数は何人月必要か。
平成27年度 秋期 ITパスポート試験 問44
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 44
Incorrectア
5 corresponds to cases such as the total when scale is mistakenly set to 2 (0.5+1+2+1+0.5 = 5). It fails to correctly derive scale = 4 from the condition that external design is 1 person-month with a productivity of 4, so the effort of every phase becomes too small.
Incorrectイ
7 is the result of omitting the effort of integration testing (2 person-months) and system testing (1 person-month), as in external design 1 + internal design 2 + programming 4 = 7. It does not sum all five phases, so it is wrong.
- ウ
正解 Since productivity = scale ÷ effort, we find effort = scale ÷ productivity. The development scale is the same value in every phase. The reference phase, external design, has a productivity of 4 and requires 1 person-month of effort, so scale = productivity × effort = 4×1 = 4. The effort for each phase is: external design = 4÷4 = 1 person-month, internal design = 4÷2 = 2 person-months, programming = 4÷1 = 4 person-months, integration testing = 4÷2 = 2 person-months, system testing = 4÷4 = 1 person-month. The total is 1+2+4+2+1 = 10 person-months, so the correct answer is “ウ”.
Incorrectエ
13 is the error of treating the productivity values directly as the effort of each phase, giving 4+2+1+2+4 = 13. It misunderstands the relationship that the higher a phase's productivity, the smaller its effort (inverse proportion).
ここがポイント
- Productivity = scale ÷ effort, that is, effort = scale ÷ productivity. Since the development scale is common to all phases, derive the scale from the reference phase and then sum the effort of each phase.
- The higher a phase's productivity, the smaller its effort (inverse proportion). The key point is not to confuse the productivity values directly with the effort.
用語