Variance Formula

About Variance Formula

Let us first define variance before understanding the variance formula. The squared variation of values (Xi) of a random variable (X) from its mean (μ) is known as variance (σ²). The variance formula allows us to calculate the spread from the random variable's mean. For a population and a sample, the variance formula is different. Get the List of all Maths formulas in one place.

The variance calculations for ungrouped data and grouped data are different. The calculations for variance are listed below.

• For ungrouped data, the variance id written as:
  • Population Variance for the population of size
  • Sample Variance for sample of size
• For grouped data, the variance is written as:
  • Population Variance, for the population of size
  • Sample Variance, for sample of size

where,

• ¯X is the mean
• Mi is the mid-point of the ith interval.

Note:

• For ungrouped data
• For grouped data,