Which visual tool is useful for showing the relationship between two quantitative variables?

A scatter diagram is an effective visual tool for illustrating the relationship between two quantitative variables. This type of graph displays points on a Cartesian plane, where each point represents an observation, with one variable plotted along the x-axis and the other along the y-axis. By visually assessing the pattern of these points, it becomes possible to identify trends, correlations, or potential causal relationships between the variables.

For example, if one were to plot the height and weight of individuals, a scatter diagram would allow you to observe if there is a trend where taller individuals tend to weigh more, which could suggest a positive correlation. The closeness of the points to a straight line can also indicate the strength of the relationship—if the points closely align along a line, this indicates a strong relationship, while a more dispersed pattern suggests a weaker or non-existent correlation.

While other visual tools, such as line graphs, histograms, and pie charts, serve different purposes, they do not effectively represent the relationship between two quantitative variables. Line graphs are primarily used to show trends over time, histograms are used for displaying the distribution of a single quantitative variable, and pie charts are effective for illustrating proportions of a whole for categorical data. Thus, the scatter diagram is uniquely suited for exploring