great question, a phd is when you continue your studies under the one on one supervision of professor in the area of your interest (e.g. for me that was pain in children). The focus is to learn all about how to design a study, collect your data and interpret your data. You also learn how to share your data with others through writing scientific articles and presenting your work at conferences. It typically takes 3 to 4 years to complete a phd.
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