Data symmetry in a statistical distribution refers to how a dataset is mirrored around its center point. Symmetrical data is balanced on both sides of its central value—like a mirror image.
The most common example is the
normal distribution, which is perfectly symmetrical. In a normal distribution, each side is a mirror image of the other, with most data points concentrated around the central mean.
On the other hand,
skewed data lacks this balance:
- Left-Skewed (Negatively Skewed): The tail on the left side is longer or fatter.
- Right-Skewed (Positively Skewed): The tail on the right side is elongated.
Identifying symmetry or skewness is important for interpreting data correctly and choosing the appropriate statistical methods.