What is the primary use of a scatter plot?

A scatter plot is primarily used to visualize and identify relationships between two numerical variables. This type of graphic representation allows analysts to see how one variable is affected by another, illustrating patterns of correlation, whether positive, negative, or nonexistent. By plotting individual data points on a Cartesian plane, the scatter plot can effectively reveal the direction, form, and strength of the relationship between the two variables.

For instance, if an analyst is examining the relationship between hours studied and exam scores, the scatter plot would display each student's hours and scores as points on the graph. By observing the clustering or dispersion of these points, the analyst can infer whether more study hours tend to correlate with higher exam scores, facilitating deeper insights into the data.

Other options serve different purposes: comparing categorical data is done through bar graphs or pie charts; displaying trends over time typically utilizes line graphs; highlighting outliers in a dataset can be done using box plots or marked points in scatter plots, but this is not the primary purpose of a scatter plot itself. Thus, the correct answer underscores the scatter plot's essential role in examining relations between numerical variables, which is fundamental in data analysis.