問27
頻出度★★★
翌月の製造量は，翌月の販売見込量－当月末の在庫量で算出される。翌月の販売見込量が，当月までの 3 か月の販売実績量の移動平均によって設定されるとき，9 月の製造量の算出式を示したものはどれか。
| 5月 | 6月 | 7月 | 8月 | 9月 | |
|---|---|---|---|---|---|
| 販売実績量 | A | C | E | G | I |
| 月末在庫量 | B | D | F | H | J |
平成21年度 春期 ITパスポート試験 問27
ストラテジ系企業活動 › 業務分析・データ利活用
This question's explanation and your answers so far.
解説
問 27
Incorrectア
The first half, (C+E+G)/3, is the moving average for June to August and is correct, but the second half is wrong because it also averages the inventory volume over 3 months as (D+F+H)/3. What the formula subtracts is the current month-end inventory volume, a balance at a single point in time, which is only H at the end of August. Inventory volume is not a flow over a period but a month-end balance, so there is no point in averaging it.
- イ
正解 What is asked for is September's production volume, so September is the next month, and the current month used as the reference is August. First, find the expected sales volume. The next month's expected sales volume is the moving average of the actual sales volume of the 3 months up to the current month, so we use the 3 months up to August, that is June, July and August, which from the table gives (C+E+G)/3. Next, subtract the inventory. The formula is: the next month's expected sales volume − the current month-end inventory volume. The current month-end is the end of August, so we subtract just the single value H, August's month-end inventory volume in the table. Inventory volume is a balance (a stock) at a month-end point in time, so there is no need to average it. Therefore September's production volume = (C+E+G)/3 − H, and イ is correct.
Incorrectウ
The moving average is taken over July, August and September (E+G+I), which is shifted by one month. The current month is August, so only the actual results up to August can be used, and September's actual sales volume I is not yet fixed at this point. In addition, the inventory volume is also averaged as (F+H+J)/3, which goes against the definition of subtracting a single current month-end inventory volume.
Incorrectエ
The form of subtracting only one inventory value is correct, but every month used is shifted by one. The moving average covers July to September (E+G+I) and includes September's actual sales volume I, which is not yet fixed, and the inventory subtracted has become J, the inventory at the end of September. At the point of calculating September's production volume, only the data up to August is known, so the average must cover June to August and the inventory must be H, the inventory at the end of August.
ここがポイント
- The mapping between the current month and the next month in: next month's production volume = next month's expected sales volume − current month-end inventory volume. The month asked about (September) is the next month, so the first step is to read the current month as the preceding month, August.
- A moving average is a demand-forecasting method that averages the actual results of the most recent 3 periods, using only the June, July and August results that are already fixed as of the current month (August). Inventory volume, on the other hand, is a month-end balance, so it is not averaged; the single value at the current month-end (the end of August) is subtracted as it is.
用語