How do university training and subsequent practical experience affect expertise in data science? to answer this question we developed methods to assess data science knowledge and the competence to formulate answers, construct code to problem solve, and create reports of outcomes. in the cross-sectional study, undergraduate students, trainees in a certified postgraduate data science curriculum, and data scientists with more than 10 years of experience were tested (100 in total: 20 each of novice, intermediate, and advanced university students, postgraduate trainees, and experienced data scientists).