A person whose job is statistics — designing how data gets collected, then working out what it honestly means. Countable noun, and the stress falls on the -ti- : sta-tis-TI-cian. It is a real profession, not just "someone good at maths." Statisticians work for governments counting the population, for hospitals testing whether a treatment works, for insurance companies, for sports teams, and increasingly in tech. A big part of the job is the unglamorous half — spotting when a number is misleading, when a sample was badly chosen, when two things move together without one causing the other. Note the -ian ending: it marks a person who does something, and English uses it for a lot of skilled trades — musician, technician, physician, electrician, librarian. Say "a statistician," not "a statistic person." These days you will often hear data scientist for closely related work; statistician is the older word and leans more toward mathematical training.