Variance and Standard deviation

Both variance and standard deviation tell the researcher how spread out the scores are and how tightly the scores are clustered around the mean.

The Standard Deviation is most commonly used because it is the square root of the variance which provides the researcher a standardized measure of the spread that is expressed in the same units as the variable. The more spread out, the higher the standard deviation.

Variance

To calculate:
Calculate the mean. Subtract the mean from each number in the dataset. Square each new number then calculate the new average.