Statistics. I kid, I kid. Hugo Bowne-Anderson, host of the DataFramed podcast, culled some information together that he’s gathered from interviewing data scientists. This is what data scientists really do.
One result of this rapid change is that the vast majority of my guests tell us that the key skills for data scientists are not the abilities to build and use deep-learning infrastructures. Instead they are the abilities to learn on the fly and to communicate well in order to answer business questions, explaining complex results to nontechnical stakeholders. Aspiring data scientists, then, should focus less on techniques than on questions. New techniques come and go, but critical thinking and quantitative, domain-specific skills will remain in demand.
Other than the best spots to nap in between classes, this is one of the most important things I learned in (statistics) graduate school.