Power BI developer use correlation analysis to examine relationships between different variables in datasets. By calculating correlation coefficients through DAX or integrating external scripts, developers can identify positive, negative, or neutral relationships between metrics like sales and marketing spend, or customer satisfaction and product returns. They visualize these relationships using scatter plots or correlation matrices, making it easy for stakeholders to understand the strength and direction of the correlations. This type of analysis helps businesses optimize resource allocation, identify drivers of performance, and uncover hidden patterns in their data.