## How do you find the semi-deviation?

Semivariance is calculated by measuring the dispersion of all observations that fall below the mean or target value of a set of data. Semivariance is an average of the squared deviations of values that are less than the mean.

**What is the difference between variance and semivariance?**

As nouns the difference between variance and semivariance is that variance is the act of varying or the state of being variable while semivariance is (statistics) a measure of the dispersion of those values that fall below the mean or target value of a data set.

**How is downside deviation calculated?**

Calculate the square root of your result. Multiply that result by 100 to calculate the investment’s downside deviation as a percentage. Concluding the example, calculate the square root of 0.000567 to get 0.0238. Multiply 0.0238 by 100 to get a 2.38 percent downside deviation.

### What is semi-deviation?

Semi-deviation is a method of measuring the below-mean fluctuations in the returns on investment. Semi-deviation will reveal the worst-case performance to be expected from a risky investment. Semi-deviation is an alternative measurement to standard deviation or variance.

**Why do we use semi-deviation instead of standard deviation?**

The semideviation starts with a simple observation: people don’t care about accidentally earning too much money, they really only care about when returns are less than expected. You calculate the average. Then you look at any values that fall below the average and see how far below the average they were.

**How do you calculate downside semi variance?**

To calculate it, we take the subset of returns that are less than the target (or Minimum Acceptable Returns (MAR)) returns and take the differences of those to the target. We sum the squares and divide by the total number of returns to get a below-target semi-variance.