問14
頻出度★★★
パレート図の説明として, 適切なものはどれか。
平成23年度 秋期 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
This describes an arrow diagram (PERT chart). It represents activities with arrows and the start and end points of activities with circles (nodes), connecting them in sequence from left to right to express the flow from start to finish; generally the required number of days is added to each arrow so that a schedule can be planned and the critical path, which is the longest route, can be found. What it expresses is the order relationship between activities, not the ranking of counts by category or cumulative ratios, so it is not a Pareto chart.
Incorrectイ
This describes a scatter diagram. The two values of two-dimensional data are plotted as points, using the vertical and horizontal axes as coordinate values, and the presence and the strength of a correlation between the two variables are read from how the points are scattered. Like the Pareto chart, the scatter diagram is one of the seven QC tools, but it is neither a bar chart nor a line chart, and it has no element of sorting in descending order of count or of displaying cumulative ratios, so it is wrong.
- ウ
正解 The correct answer is ウ. A Pareto chart is a combination chart in which the number of occurrences of defects, complaints, and the like is tallied by classification category (cause, phenomenon, and so on), the categories are arranged from the left in descending order of count as a bar chart, and a line chart showing the cumulative sum of each category’s ratio to the total count (the cumulative composition ratio) is overlaid on top of it. Choice ウ, “a diagram that shows data classified by category arranged in a bar chart in descending order of count, overlaid with a line chart showing the cumulative sum of the ratio to the total count”, states exactly this definition (a descending bar chart plus a cumulative-ratio line), so it is appropriate. Because the categories with the largest counts gather on the left, the tendency for a few top items to account for most of the whole (the so-called 80-20 rule) can be read at a glance, and the chart is used for priority-oriented analysis such as choosing the items up to the point where the cumulative line reaches 70 to 80 percent as the targets of focused countermeasures. ABC analysis, which divides items into ranks A, B, and C by cumulative ratio, is also a technique built on this chart.
Incorrectエ
This describes a radar chart (spider chart). The value of each item is taken on one of several numerical axes extending radially from the center, and those points are connected with lines to draw a polygon; it is suited to viewing the balance among several items or comparing them with standard values. Because its axes are arranged radially, it is not in the first place a bar chart arranged from the left in descending order of count, and it has no cumulative-ratio line either, so it cannot be a description of a Pareto chart.
ここがポイント
- Definition of a Pareto chart: a combination chart in which the counts by classification category are arranged in a bar chart in descending order of count, overlaid with a line chart showing the cumulative sum of the ratio to the total count. It is used for priority-oriented analysis that concentrates countermeasures on the top items, and as the basis for ABC analysis.
- Telling the seven QC tools apart from related diagram methods: the seven QC tools are the Pareto chart / cause-and-effect diagram (fishbone diagram) / histogram / scatter diagram / control chart / check sheet / stratification (graphs). Among the incorrect choices in this question, the arrow diagram is one of the new seven QC tools (N7), a diagram used for schedule planning and for finding the critical path, while the radar chart is not included in the seven QC tools at all and is a general-purpose graph used to compare the balance among several items; remember both as a separate group outside the seven QC tools.
用語