問50
頻出度★★★
品質の目標に対し，不良が多く発生しているシステム開発プロジェクトがある。重点的に解消すべき課題を明らかにするために，原因別に不良の発生件数を調べ，図で表すことにした。このときに用いるのが適切な図はどれか。
平成28年度 秋期 ITパスポート試験 問50
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 50
Incorrectア
A cause-and-effect diagram (fishbone diagram) organizes and lists the possible factors for a given result (characteristic) by branching them out like the bones of a fish. It helps in brainstorming causes, but it cannot count the number of occurrences of each cause or arrange them in descending order to show priority, so it does not fit the purpose of clarifying priority issues by count. Chart ア is also skeleton-shaped and carries no count information.
- イ
正解 The correct answer is イ, the Pareto chart. A Pareto chart arranges items (here, the causes of defects) as bars from left to right in descending order of occurrence count, and overlays a line showing their cumulative percentage. Because it makes clear at a glance that a small number of causes with large counts account for most of the total, it is ideal for identifying the issues that should be addressed as priorities, namely the top major causes, and it corresponds exactly to the idea of priority management (ABC analysis). Chart イ also has the typical Pareto shape, with taller bars on the left getting smaller toward the right and a cumulative line extending toward the upper right, so it can express both the count by cause and the prioritization at the same time.
Incorrectウ
A scatter plot places two kinds of paired data on the vertical and horizontal axes as points, and is used to examine whether there is a correlation between two variables and how strong it is. It is not meant for aggregating counts by cause to show priority, so it is inappropriate. Chart ウ likewise looks at correlation through the scatter of points and cannot compare counts by cause.
Incorrectエ
A flowchart represents the steps and branching flow of processing or work by connecting symbols. It expresses the flow of a process and is unrelated to the purpose of aggregating defect counts by cause to narrow down priority issues. Chart エ likewise only shows the flow of start, process, decision, and end, and does not deal with counts.
ここがポイント
- Pareto chart = a chart that arranges items as bars in descending order of count and overlays a line for the cumulative percentage. It is used to identify the small number of top priority items (ABC analysis).
- Distinguishing the typical QC charts: listing and organizing causes = cause-and-effect diagram, prioritizing by count = Pareto chart, correlation between two variables = scatter plot, expressing steps = flowchart.
用語