A scatter diagram helps to determine whether there is a relationship between two variables.

• A. It shows distribution of a single variable
• B. It determines if there is a relationship between two variables
• C. It lists steps in a process
• D. It compares means of groups

Answer: (B)

A scatter diagram plots two quantitative variables against each other to reveal whether a relationship exists between them. Each point represents a paired observation, with one variable on the horizontal axis and the other on the vertical axis. If the points tend to form a pattern that slopes upward, the variables move together (positive relationship); if they slope downward, one tends to increase as the other decreases (negative relationship). The tighter the pattern around a line or curve, the stronger the relationship; widely scattered points suggest little or no linear relationship. Outliers can also appear and signal unusual data points or errors. A key caveat: a relationship seen in a scatter diagram does not prove causation.

This tool isn’t used to show the distribution of a single variable (that would be a histogram or similar), it isn’t used to list steps in a process (that’s a flowchart), and it isn’t used to compare means of groups (that’s typically a bar chart or box plot).