問46
頻出度★★★
図のアローダイアグラムで示される日程のプロジェクトが開始されてから5週が経過した。各工程の進捗率が表に示すとおりの場合，プロジェクト完了の遅延につながる工程はどれか。ここで，今後の各工程の作業は，当初の予定どおり進むものとする。
| 工程名 | A | B | C | D | E | F | G |
|---|---|---|---|---|---|---|---|
| 進捗率（％） | 100 | 80 | 100 | 100 | 25 | 0 | 25 |
平成22年度 秋期 ITパスポート試験 問46
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 46
Incorrectア
B takes 5 weeks and is planned to finish in week 5, but its actual progress is 80% (= 4 weeks of work), so it is indeed one week behind. However, the path B→F that B belongs to is 5+4 = 9 weeks, which has one week of float against the 10-week critical path. Even if B ends in week 6, F can start in week 6 and finish in week 10 after 4 weeks, still meeting the overall 10 weeks. Because the delay stays within the float, it does not lead to a delay in project completion.
Incorrectイ
E starts in week 4, after A is finished, and takes 4 weeks, so its planned progress at the 5-week point is one week of work = 25%. The actual progress is also 25%, exactly on plan, so it is not behind at all. Proceeding this way it finishes in week 8, leaving two weeks of float against the overall 10 weeks.
Incorrectウ
F cannot start until week 5, when its predecessor tasks (B and D) are all complete, so being at 0% at the 5-week point is exactly as planned and is not a delay. Even if it starts in week 6 because of B's one-week delay, it takes 4 weeks and finishes in week 10, so it does not delay the overall completion. The key point is not to misread the 0% of a task that has not started yet as being behind schedule.
- エ
正解 The correct answer is エ (task G). First, read the schedule from the diagram. There are four paths from start to finish: A→E = 4+4 = 8 weeks, A→D→F = 4+1+4 = 9 weeks, B→F = 5+4 = 9 weeks, and C→G = 2+8 = 10 weeks. The longest of these, C→G at 10 weeks, is the critical path, so the originally planned completion is 10 weeks. Next, find the planned progress at the 5-week point. G starts in week 2, after C is finished, and takes 8 weeks, so by week 5 it should have completed 3 weeks of work = 37.5%. The actual progress, however, is only 25% (= 2 weeks of work), which is one week behind. G lies on the critical path, where the float (slack) is zero, so this one-week delay turns directly into a delay of the whole project. Even if the remaining 75% = 6 weeks proceeds as planned, completion comes at 5+6 = 11 weeks, one week later than the original 10 weeks. Therefore the task that leads to a delay in project completion is G.
ここがポイント
- In schedule management with an arrow diagram, first calculate the duration of every path and identify the longest one, the critical path. In this question C→G at 10 weeks is the critical path, and the tasks on it have zero float (slack), so a delay there turns directly into a delay of the whole project.
- Progress rates must be judged by comparing them with how far the work should have advanced by that point in time. A task sitting at 0% before its planned start is not behind, and conversely a delay on a path that has float does not affect the whole project as long as it stays within that float. Whether a delay matters is decided by whether the task is on the critical path and by how much float it has.
用語