**Central Tendency** tells you about the centers of the data. Useful measures include the mean (Weighted Mean, Harmonic Mean, Geometrical Mean), median, and mode (Mode, Multimode).

**Harmonic Mean**is the reciprocal of the arithmetic mean of the reciprocals. $\frac{n}{\sum_i^n(\frac{1}{x{i}})}$ , where $i=1,2,...n$ and $n$ is the number of items in the dataset $x$ .**Geometric Mean**is the`n-th`

root of the product of all $n$ elements $x_i$*in a dataset*$x$*.*$\sqrt[n]{\prod_i^n x_{i}}$ , where $i=1,2,...n$ and $n$ is the number of items in the dataset $x$ .

**Variability** tells you about the spread of the data. Useful measures include variance, Standard deviation, Skewness, Percentile, and Range.

**Correlation or Joint Variability** tells you about the relation between a pair of variables in a dataset. Useful measures include covariance and the correlation coefficient.