Skewness
The most commonly used tool to measure asymmetry is Skewness
Skewness indicates whether the observations in a dataset are concentrated on one side.
There are three types of skewness: positive/right skew, zero skew & negative/left skew.
The formula for skewness is not important as it will be calculated by the program itself. The formula for calculating skew in Excel is =skew(dataset)
The direction of the skew is dependent on which side the tail is leading to.
Positive/Right skewness:
In a dataset, if Mean > Median, it is considered positive skew. The outliers lie towards the right side in a positive skew.
Zero/No skewness:
In a dataset, if Mean = Median = mode, it is considered zero/no skew. The outliers lie symmetrically on both sides.
Negative/Left skewness:
In a dataset, if Mean < Median, it is considered Negative skew. The outliers lie towards the left side in a negative/left skew.
Skewness tells us a lot about where the data is situated. Measures of Asymmetry like skewness are the link between central tendency measures and probability theory which helps us get a more complete understanding of the data we are working on.