問30
頻出度★★★
ある作業を 6 人のグループで開始し, 3 か月経過した時点で全体の 50% が完了していた。残り 2 か月で完了させるためには何名の増員が必要か。ここで, 途中から増員するメンバの作業効率は最初から作業している要員の 70% とし, 最初の 6 人のグループの作業効率は残り 2 か月も変わらないものとする。
平成21年度 秋期 ITパスポート試験 問30
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 30
Incorrectア
With only 1 additional person, the extra output is about 1.94% per month, which does not cover the shortfall of 8.33% per month at all. After 2 months the progress is about 50% + (16.7 + 1.94) × 2 ≈ 87%, so the work cannot be finished by the deadline.
Incorrectイ
Even with 3 additional people, the extra output is only 1.94 × 3 ≈ 5.83% per month, which falls short of the required 8.33% per month. The total is about 22.5% per month, so in 2 months only 45% is completed, which does not reach the remaining 50%.
Incorrectウ
The value 4 comes from rounding 4.29 people down. The extra output is 1.94 × 4 ≈ 7.78% per month, slightly below the required 8.33% per month, and the total output over 2 months is about 48.9%, which does not reach 50%. The required number of people must always be rounded up.
- エ
正解 Treat the whole amount of work as 100%. Since 6 people completed 50% in 3 months, the output of one original member per month is 50% ÷ (6 people × 3 months) = 25/9 % ≈ 2.78%. To finish the remaining 50% in 2 months, a pace of 25% per month is required. However, the original 6 people alone can produce only 6 × 25/9 = 50/3 % ≈ 16.7% per month, so 25 − 50/3 = 25/3 % ≈ 8.33% is missing each month. The efficiency of an added member is 70% of an original member, so each added person produces 25/9 × 0.7 = 35/18 % ≈ 1.94% per month. The number of people needed is (25/3) ÷ (35/18) = 30/7 ≈ 4.29 people, and since people cannot be counted in fractions, this is rounded up to 5. Therefore the correct answer is エ, 5 people.
ここがポイント
- The basis of staffing planning is the relation work amount = number of people × efficiency × period. First find the output per person per month (productivity) from the actual results, then derive the required monthly pace from the remaining work and the remaining period, and calculate how many people are needed to close the gap.
- When adding members whose efficiency differs, do not simply add the head count; convert them into an effective number of people by multiplying by the efficiency factor. Also, when the required number of people has a fractional part, it must be rounded up in order to meet the deadline.
用語