A data analysis system analyzes data sets that are characterized by a wide variety of probability density functions (PDFs), and also analyzes mixed populations, i.e., a single data set containing subsets of data that each fit a different distribution. The data analysis system receives quality control data from a product manufacturing or product testing floor, determines whether the data is a mixed population, and fits the data with a variety of PDFs. The data analysis system selects the best fitting PDF based on statistical characteristics calculated for each fitted PDF. The data analysis system generates performance capability parameters based on the best fitting PDF, and may generate reports illustrating the performance capability parameters. The data analysis system also adjusts statistical control limits to provide a more reliable process trigger and control plan. In this manner, the data analysis system may more accurately report product performance.