Research Methods in Political Science Practice Exam

Percentiles describe where a value falls in an ordered data set. The 50th percentile is the value such that half the observations are at or below it. That makes it the median. The mean is the arithmetic average, not a percentile; the range is the spread between the smallest and largest values, not a position in the ordered list; the mode is the most frequent value, not a central position. In practice, the 50th percentile and the median coincide—the median is the central point of the data (for even-sized samples, it's the average of the two middle values). For example, in 2, 3, 5, 7, 9, the 50th percentile/median is 5.