What is the difference between the 25th and 75th percentiles called?

The term that describes the difference between the 25th and 75th percentiles is known as the interquartile range. This range is a measure of statistical dispersion and provides insight into the spread of the middle 50% of a data set. By focusing on the values that fall between the first quartile (25th percentile) and the third quartile (75th percentile), the interquartile range helps to eliminate the influence of outliers and extreme values, which can skew the results if one were to look solely at the complete range of the data. This metric is particularly useful in descriptive statistics when assessing how values are distributed within a dataset.

In contrast, variance measures how far a set of numbers is spread out from their average value, while standard deviation is the square root of variance, also indicating spread but in the same units as the data. Percentile rank, on the other hand, indicates the percentage of scores in a distribution that a particular score is greater than or equal to, but it does not refer to the distance between specific percentiles. Thus, the interquartile range provides a distinct and focused way to understand the central tendency and variability of the data compared to the other statistical measures presented.