For what purpose are scatter plots primarily used?

Scatter plots are primarily used to investigate relationships between two or more variables, making answer B the correct choice. These graphical representations allow analysts to visualize how one variable correlates with another, revealing patterns, trends, or potential outliers within the dataset. By plotting individual data points on a Cartesian plane, scatter plots provide valuable insights into the strength and direction of the relationship, which can suggest whether an increase in one variable results in an increase or decrease in another.

Other options, while useful in different contexts, do not serve the primary purpose of scatter plots. Cumulative data over time is typically displayed through line graphs, as they effectively illustrate trends across time periods. Representing parts of a whole is best achieved with pie charts or stacked bar charts, which visually break down components of a total. Analyzing time series data often relies on line graphs, which can track changes over intervals and highlight temporal patterns more clearly than scatter plots. Thus, scatter plots stand out specifically for their ability to explore and clarify relationships between multiple variables.