How do researchers determine what is true based on the data they collect? This question is one of the central concerns of statistics, which uses mathematical models to draw useful conclusions about the real world.

Germany, officially the Federal Republic of Germany, is a federal parliamentary republic in western-central Europe. The country consists of 16 states, and its capital and largest city is Berlin.

The PhD is a doctoral degree, specifically called a "doctor of philosophy" degree. This is misleading because PhD holders are not necessarily philosophers (unless they earned their degree in philosophy!). That said, PhD recipients are able to engage in thought experiments, reason about problems, and solve problems in sophisticated ways.