Central Tendency, Asymmetry, and Variability

The Central Tendency is measured by 3 parameters:

• Mean: Average

• Median: Mid point

• Mode: The most frequent

Credit: https://www.onlinemathlearning.com/population-mean.html

The most common method to measure Asymmetry is so called the Skewness. There are 3 types of skewness our data can hold:

• Zero Skew: the data are symmetric and form a bell shape

• Negative (Left) Skew: the left-tailed, the outliers are on the left-side

• Positive (Right) Skew: the right-tailed, the outliers are on the right-side

Credit: https://study.com/academy/lesson/skewness-in-statistics-definition-formula-example.html

The skewness tells us where our data are mostly situated and acts as a bridge between the Central Tendency and Probability Distribution.

Note that the skewness may be hard to see especially when we use wide bin sized histograms. Therefore it is best to use the mathematical formula to see how skewed our data set is.

The Variability (Dispersion/Spread/Variance) is calculated separately per Sample and Population.

Sample Variance

Population Variance

Why is it Squared?

1. Dispersion is non-negative

2. Non-negative values do not cancel out

3. Amplifies the effect of large differences