問94
頻出度★★★
A さんは，製品 N の売上の動向を分析するため，昨年と今年の売上高の推移を基に，表計算ソフトを用いて図1のワークシートを作成した。 図1の D 列の移動合計欄には，当該月を含む過去12か月の売上の合計を，E 列の売上累計欄には今年の売上高の累計を計算する式が入力されている。また，製品 N の売上の動向を視覚的に確認するため，図2の売上高の推移グラフを作成した。 図2中の(a)で示される折れ線から読み取れることとして, 適切なものはどれか。
平成25年度 春期 ITパスポート試験 問94
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 94
Incorrectア
What shows the cumulative total of this year's sales is column E of Figure 1, which in Figure 2 corresponds to the line of black diamonds (◆). The cumulative line starts from the small value of 3,200 thousand yen in January, piles up each month's sales, and only reaches 70,300 thousand yen in December, forming a line that climbs steeply from the lower left to the upper right. In contrast, (a) already starts from a height of about 60,800 thousand yen in January and moves only about 10,000 thousand yen over the 12 months, making it a gentle line whose starting height and slope are both completely different from the cumulative line. The cumulative line is drawn in Figure 2 as a separate series, so (a) cannot be read as the cumulative total of this year's sales.
Incorrectイ
A growth rate is a ratio, and its unit is a percentage or a multiple, but the vertical axis of Figure 2 has only a money scale of sales (thousand yen); there is no axis from which a rate can be read. Figure 1 likewise has no column that calculates a year-on-year comparison: column D is the moving total and column E is the cumulative sales. It is true that the increase of the moving total over the previous month equals “this year's sales for that month minus last year's sales for that month,” so the difference in amount from the same month of last year is reflected in it. However, that is only a difference in amount, not a ratio showing by what percentage sales grew. Therefore the growth rate compared with the same period last year cannot be known from the (a) line.
- ウ
正解 The correct answer is ウ. What (a) points to in Figure 2 is the line of white squares (□) at the very top of the graph. It already starts from a high position of about 60,800 thousand yen in January and rises gently to the upper right, reaching 70,300 thousand yen in December. This sequence of values matches exactly the moving total in column D of Figure 1 (60,800 → 61,100 → 62,400 → … → 70,300), so (a) can be identified as the line that represents the moving total (moving annual total). As the passage states, the moving total is the sum of sales for the past 12 months including the current month, so every point is always an amount that adds up to exactly one year. Once one full year is summed up, the monthly and seasonal peaks and troughs — selling well in March and dropping in June and July — cancel each other out and disappear, and all that remains is the movement of the sales level itself. The (a) line in Figure 2 rises consistently from 60,800 thousand yen to 70,300 thousand yen, which shows that even after seasonal factors are removed, the sales scale of Product N keeps growing. In other words, what can be read from (a) is the long-term trend of sales, so ウ is appropriate.
Incorrectエ
What shows the tendency of sales fluctuation by month, season, and the like are the two lines that move finely up and down in the lower part of Figure 2, namely this year's sales (white circles ○, column C) and last year's sales (black triangles ▲, column B). Both form a large peak in March (13,200 thousand yen this year, 11,900 thousand yen last year) and a small peak in August (9,200 thousand yen this year, 8,000 thousand yen last year), so the busy and slack months appear clearly. In contrast, the moving total of (a) always adds up 12 months together, so seasonal peaks and troughs cancel out and the line becomes flat. It is in fact a line used precisely to remove seasonal fluctuation, so the tendency of monthly or seasonal fluctuation cannot be read from it.
ここがポイント
- The moving total (moving annual total) is the value obtained by summing the sales of the past 12 months including the current month. Because it always adds up exactly one year, monthly and seasonal fluctuations cancel out, so it is used to judge the long-term trend of sales (rising, flat, or falling). Its increase or decrease from the previous month equals “this year's sales for that month minus last year's sales for that month,” so a moving total that rises to the right means that months exceeding the same month of the previous year are continuing.
- In a combination chart for sales analysis (three lines overlaid look like the letter Z, which is why it is called a Z chart), each line tells you something different. The monthly sales line shows fluctuation by month and season, the cumulative sales line shows the build-up from the start of the period and the degree of goal achievement, and the moving total line shows the long-term trend. Which line is which can be told from the height of its starting point and its shape (the cumulative line starts near 0 and climbs monotonically, while the moving total starts at a high position and moves gently).
用語