問29
頻出度★★★
製造業 A 社では，翌月の製造量を次の計算式で算出している。 翌月の製造量 ＝ 翌月の販売見込量 − 当月末の在庫量 ＋ 20 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法によって算出されるとき，9 月の製造量は幾らか。
| 5月 | 6月 | 7月 | 8月 | |
|---|---|---|---|---|
| 販売実績量 | 110 | 100 | 90 | 95 |
| 月末在庫量 | 10 | 10 | 35 | 25 |
平成24年度 秋期 ITパスポート試験 問29
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 29
- ア
正解 The correct answer is ア (90). First, translate the terms next month and the current month in the formula into the case of finding September's production quantity: next month = September, current month = August. (1) September's forecast sales: since it is the moving average of the actual sales of the 3 months up to the current month, the target months are June, July and August. (100 + 90 + 95) ÷ 3 = 285 ÷ 3 = 95. (2) End-of-current-month inventory: this is the end-of-month inventory for August, so 25. (3) Substitute into the formula: September's production = 95 − 25 + 20 = 90. Therefore the answer is 90, that is ア. The meaning is easier to grasp if you think of it this way: out of the forecast demand of 95, subtract the part that can be covered by the 25 units already in stock, and add 20 in order to leave 20 units of inventory at the end of the month.
Incorrectイ
92 is a value that does not come out even when the figures in the table are correctly substituted into this formula. The candidates for the moving average are only 95 (June to August) or 100 (May to July), and applying −25 +20 to them yields only 90 or 95. If you averaged over the most recent 2 months (90 and 95) instead of 3 months, you would get the close value 92.5, but the question explicitly states a 3-month moving average, so this is wrong.
Incorrectウ
95 is September's forecast sales itself (the moving average of June to August), not the production quantity. It is the value you get by taking the forecast sales directly as the production quantity without making the inventory adjustment (− the end-of-current-month inventory of 25, + 20). Also, if you shift the target period to May through July, obtain an average of 100 and compute 100 − 25 + 20, you again get 95, but that too is a misreading of the 3 months up to the current month (August).
Incorrectエ
100 is the average of the actual sales for May, June and July (110, 100, 90), a value obtained by shifting the target period of the moving average by one month. On top of that, the inventory adjustment (−25 +20) has not been made either. The 3 months up to the current month means June to August, which includes August, and it must always include the latest actual figure of 95.
ここがポイント
- Demand forecasting by the moving average method: a technique that takes the simple average of the actual figures of the most recent n periods as the forecast for the next period. Here the 3 months up to the current month means June, July and August, and does not include September, the month being forecast. Shifting the target period by one month changes the answer, so always count the most recent 3 months including the current month.
- Calculating the required quantity (production quantity): production = forecast demand − stock on hand + target inventory. Stock you already hold does not need to be produced, so it is subtracted, while the inventory you want to keep at the end of the period is produced on top of that. This is a basic idea of inventory management. The inventory subtracted here is the 25 at the end of the current month (end of August), not the inventory of any other month.
用語