Glossary term
Skew
A lopsided distribution: values pile up on one side and stretch out in a long tail on the other.
Visual intuition
30
31
32
33
most values
mean pulled right
300
One extreme value can drag summaries away from the cluster
Skew is the lopsided stretch: the cluster sits on one side while a long tail pulls the mean toward it.
Example
In 30, 31, 32, 33, and 300, the single 300 drags the up to 85.2 while the stays at 32 — the signature of right skew.
How It Works
Most households earn something modest; a few earn millions. That long right tail is skew — the pile sits left while stragglers stretch right, dragging the above the . A left skew mirrors it: think exam scores when most students do well. Whenever mean and median disagree noticeably, skew is usually the reason, and the median is usually the fairer 'typical' value.
Concepts
Averages Mislead
The mean adds everything up and divides, so a few extreme values can drag it far from the typical case. In skewed data the median — the middle value — better represents what is normal. Ask about the shape of the data, not just its average.
Summary Statistics
Summary statistics compress a dataset into numbers such as the mean, variance, correlation, or regression line. They are useful, but they can hide shape, outliers, clusters, and curved relationships that a graph would reveal immediately.
Related Facts
Data Tricks
4 min · easy
Most people earn less than the average wage
In a lopsided economy, a handful of huge incomes pull the 'average' above what a typical person actually makes.
Data Tricks
5 min · easy
Mean vs median: which average should you use?
The mean shares the total equally. The median finds the middle case. In skewed data, those can tell very different stories.