問49
頻出度★★★
プロジェクトの開始から完了まで最も所要時間が掛かるクリティカルパスを見つけるのに使う図として, 適切なものはどれか。
平成24年度 秋期 ITパスポート試験 問49
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 49
- ア
正解 The correct answer is “ア Arrow Diagram”. An arrow diagram (PERT chart) represents each task that makes up a project as an arrow, and the start and end points of tasks as junction points (nodes), drawing the order relationships among tasks and the number of days each requires in the form of a network. In this diagram there are several paths from the start to the completion, but by totaling the time required for each path and comparing them, you can find the path that takes the longest time. That is the critical path, and if a task on it is delayed even by a single day, the completion of the entire project is delayed by the same amount. Conversely, paths other than the critical path have spare days (float), so they can absorb delays to some extent. Therefore, the diagram that directly serves the purpose of “finding the path that takes the longest time” is the arrow diagram.
Incorrectイ
A Pareto chart lines up items such as defects or failures as bars in descending order of the number of occurrences, and overlays their cumulative percentage as a line; it is one of the seven QC tools. It is a quality-control diagram used to see “which items account for most of the whole” and thereby narrow down where to focus improvement. It can express neither the order relationships among tasks nor the time they require, so it cannot be used to find the critical path.
Incorrectウ
A histogram divides measured values into several intervals (classes) and shows the number of data items falling into each interval as bars. It is a diagram for grasping the variation of data and the shape of their distribution, and it carries no ordering relationship among tasks, so it cannot be used to total the time required for paths and identify the critical path.
Incorrectエ
A milestone chart plots on a time axis the dates that form the turning points of a project (milestones), such as completion of design, start of testing, or delivery. It is suitable for managing the planned and actual dates of important checkpoints, but it does not comprehensively express the dependencies among individual tasks or the time they require, so it cannot be used to trace paths and calculate the longest one.
ここがポイント
- Critical path = on an arrow diagram (PERT chart), the path among all paths from start to completion whose total required time is the largest. Tasks on this path have no slack, so a delay there directly becomes a delay of the whole project.
- Keep the different uses of the diagrams straight: an arrow diagram for analyzing schedules and task order, a Pareto chart for narrowing down priority items, a histogram for grasping the distribution of data, and a milestone chart for managing the dates of key checkpoints.
用語