A reusable D3 scatter plot displays the relationship between study hours and test scores, with points colored by treatment or control group using a categorical color scale. The chart loads CSV data with `d3.csv` and `d3.autoType`, then renders axes, labels, and circles through a factory function that sets width, height, and accessors via chained setters. D3 v7 handles scales (`d3.scaleLinear`, `d3.scaleOrdinal`) and axes (`d3.axisBottom`, `d3.axisLeft`) within a joined SVG structure.