It is a common misconception that standard deviation must be positive. In fact, it can be negative as well. Standard deviation is calculated using the variance of a data set and is used to measure how much variation there is in the data set. The more spread out your data points are on either side of the mean, the higher your standard deviation value will be.

Standard deviation can be positive, negative or 0. It is calculated using the variance of a data set and measures how much variation there are in your data points. The more spread out they are on either side of the mean, the higher your standard deviation will be and vice versa if they’re clustered together around one point.

Caution: If you have an even number of values for a population, then the standard deviation might not make sense mathematically because it cannot be broken down into halves (positive half vs negative). For example, if I had 12 numbers where half were -0.01 and others were +0.02 but my sum was zero as well (-0.01 + 0.02).