The standard deviation of a set of data is a measure of the amount of variation or dispersion of the data. To calculate the standard deviation, you need to follow these steps:

1. Find the mean (average) of the data set.
2. Subtract the mean from each data point to find the deviation for each data point.
3. Square each deviation.
4. Sum all the squared deviations.
5. Divide the sum of the squared deviations by the number of data points in the set.
6. Take the square root of the result from step 5 to find the standard deviation.

Here is the formula for calculating the standard deviation of a set of data:

σ = sqrt((Σ(x_i – μ)^2) / n)

Where: σ is the standard deviation x_i is each data point in the set μ is the mean of the data set n is the number of data points in the set Σ is the sum of the deviations.

Note that the standard deviation is expressed in the same units as the data.