Resistant measure
SAT glossary · Course Foundations
Definition
A statistic that an extreme value barely moves. The median and the mode are resistant; the mean, range, and standard deviation are not. When an item describes a data set with an extreme value and asks which measure best represents a typical value, the answer is the median — and when it asks which measure changes most if the largest value grows, the answer is the mean.
Resistant measure in plain English
A 'resistant' statistic is one that barely budges even if you throw in one wildly extreme, unusual value — it resists being dragged around by outliers. The median and the mode are both resistant, because they only care about POSITION or repetition, not the actual size of extreme values. The mean, the range, and the standard deviation are all NOT resistant — they get pulled hard by even a single extreme number. So if a question describes a data set that has an outlier and asks which measure best represents a 'typical' value, the median is the safe answer; but if it asks which measure changes the MOST if the biggest value gets even bigger, the mean is the one that moves.
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