問52
頻出度★★★
プロジェクトマネジメントにおける WBS の要素分解に関する記述のうち, 適切なものはどれか。
平成22年度 秋期 ITパスポート試験 問52
マネジメント系プロジェクトマネジメント › プロジェクトマネジメント
This question's explanation and your answers so far.
解説
問 52
- ア
正解 The correct answer is ア. A WBS (Work Breakdown Structure) is the result of breaking a project's deliverables and work down step by step from the top and organizing them into a hierarchy. The criterion for deciding where to stop this decomposition is whether, for each element at the lowest level (a work package), you can estimate the effort and cost required, and you can set a start date, an end date and a person in charge so that a schedule can be built. If a chunk is left so large that it can be neither estimated nor scheduled, neither progress nor cost can be managed. Conversely, once you have gone down to a granularity where both of those are possible, you can assign a cost, a duration and a responsible person to each work package and add them up to produce the total cost and the overall schedule of the whole project. In other words, the level of detail at the lowest level of decomposition should be one at which cost estimation and schedule development can be performed, so ア is correct.
Incorrectイ
The level of detail of decomposition is decided according to the size and complexity of the project and how finely it must be managed, so saying it should be the same regardless of project size is wrong. A small project lasting a few months with a handful of people and a large project running for years across multiple sites differ in the amount of work to be managed and in their organization, so the granularity of work packages naturally differs too. The criterion is always whether estimation, scheduling and assignment of responsibility are possible at that unit, not a uniform depth fixed in advance.
Incorrectウ
The depth of decomposition does not have to be the same for every deliverable. A deliverable that the team is used to producing and whose content is clear can be managed with shallow decomposition, while parts with high uncertainty or split among several people cannot be estimated or tracked unless they are broken down further. It is also common to leave later stages as a rough outline because their content is not fixed yet and to detail them as the start date approaches (progressive elaboration), so it is natural for the depth to differ from element to element.
Incorrectエ
It is not true that the finer the decomposition, the higher the efficiency. The finer you break things down, the more work packages there are, and each one generates management work and documents such as estimation, scheduling, progress reporting and progress roll-up. Beyond a certain point the management cost outweighs the benefit and work efficiency actually drops. The principle is to stop decomposing once you reach a manageable unit; subdividing is not an end in itself.
ここがポイント
- A WBS (Work Breakdown Structure) hierarchically decomposes a project's deliverables and work, and the elements at the lowest level are called work packages. The criterion for where to stop decomposing is whether that unit has reached a level of detail at which cost (effort and expense) can be estimated, a schedule can be developed, and a responsible person can be assigned.
- The depth of decomposition is not uniform. It should be varied according to the size and complexity of the project, the uncertainty of each deliverable, and how finely the work must be managed; decomposing too finely increases management effort and becomes counterproductive.
用語