## Variability

- Variability describes how far apart data points lie from each other & from center of the distribution
- Variability is also referred as spread, scatter or dispersion & is most commonly measured with the following
- Variance: Variance measures the dispersion of set of data points around the mean
- Standard deviation: average distance from mean

- We would have different formulas for
- Population Data
- Sample Data

- Variance:
- Population Variance:
- Formula:

- Sample Variance:
- Formula:

- Population Variance:
- Lets calculate variance for a sample data Refer Here
- Standard Deviation
- Sample Standard Deviation formula
- Population Standard Deviation formula

- You have the annual personal income from 11 people from Hyderabad. Decide whether you need to use sample or population formula for variance.
- Calculate the variance and standard deviation
- Refer Here for the excel

- Coeffecient of variation:
- This is referred as relative standard deviation
- Formula:
`standard deviation/mean`

- Refer Here this excel sheet and calculate standard deviation for new york and hyderabad pizza prices

- Exercise: Calculate standard deviation and coefficient of variation for the following excel Refer Here