VARIABILITY

Variability is the difference between what is expected and the actuals. Its purpose is to measure the dispersion between the two.

There are a number of calculations to determine variance: range, mean deviation, and standard deviation.

The range is the difference between the highest and lowest observations. The mean deviation is an observation’s value subtracted from the mean. The standard deviation measures the dispersion about the mean.

The range gives the spread between the highest and lowest value. The mean deviation determines how much an observation varies from the mean. The standard deviation determines the how far individual observations are from the arithmetic mean.

for Calculating Variability

• The formulas for calculating all three values are:

Range = Highest Value – Lowest Value