問14
頻出度★★★
ABC 分析で使用する図として, 適切なものはどれか。
平成26年度 春期 ITパスポート試験 問14
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 14
Incorrectア
A control chart plots quality characteristics such as product dimensions or defect rates in time order and draws a center line together with upper and lower control limit lines, in order to monitor whether the process is in a stable state (whether abnormal variation is occurring). It is meant for looking at the stability of a process over time; it has no function for sorting items in descending order and classifying them into A, B, and C by cumulative composition ratio, so it cannot be used for ABC analysis.
Incorrectイ
A scatter plot takes two paired sets of data (for example, temperature and sales, or working hours and the number of defects) on the vertical and horizontal axes, plots them as points, and is used to examine whether there is a correlation between the two. What it deals with is the relationship between two variables, not the ranking of items by size or the cumulative composition ratio, so it does not work as a tool for ABC analysis, which picks out the items to be managed with priority.
Incorrectウ
A cause-and-effect diagram organizes the conceivable factors behind a given result (characteristic) into the shape of a fish skeleton — a backbone with large and small bones — so as to draw them all out; it is also called a fishbone chart. It is a qualitative diagram for systematically enumerating candidate causes, and it does not express the size of numeric values or the cumulative composition ratio, so it is not suited to ABC analysis, which ranks items into A, B, and C.
- エ
正解 The correct answer is エ (Pareto chart). ABC analysis is a technique that arranges items such as inventory items, products, or defect causes in descending order of amount or count, classifies them into the three groups A, B, and C according to the composition ratio accumulated from the top (the cumulative ratio), and concentrates management effort on group A, which has the greatest impact. The chart that expresses these two operations — “sort in descending order” and “look at the cumulative composition ratio” — exactly as they are is the Pareto chart, which draws on one and the same chart a bar graph of the items sorted in descending order of value overlaid with a line graph of the cumulative composition ratio (the Pareto curve). Because the boundaries can be read off the vertical axis of the line — for example, up to 70% cumulative is A, up to 90% is B, and the rest is C — it is the most appropriate means of charting for ABC analysis. Behind the Pareto chart lies the idea that most of an overall result is produced by a small number of items (the Pareto principle, the so-called 80-20 rule), and it is worth noting that this matches exactly the purpose of ABC analysis, namely priority management.
ここがポイント
- ABC analysis is a priority-management technique that arranges the target items in descending order of amount or count, classifies them into the three ranks A (priority management), B, and C by cumulative composition ratio, and varies how much management effort is applied according to importance. It is used for inventory management, sales analysis, narrowing down defect causes, and the like.
- A Pareto chart is a chart that combines a bar graph of items sorted in descending order of value with a line graph of the cumulative composition ratio, and it is used for charting in ABC analysis. It is a good idea to sort out how it differs from the other charts among the seven QC tools: a control chart monitors process stability over time, a scatter plot grasps the correlation between two variables, and a cause-and-effect diagram draws out factors.
用語