Calculate the mean of the list of numbers by summing them together and then dividing that sum by the total quantity of numbers. Using an example, if the sample group consisted of 3,4,5,7 then the mean is (3 + 4 + 5 + 7) / 4 = 4.75.
Subtract the mean from each number to calculate their individual deviations. Using the example, calculate (3 - 4.75) = -1.75, (4 - 4.75) = -0.75, (5 - 4.75) = 0.25, and (7 - 4.75) = 2.25.
Square each of the calculated individual deviations. Using the example, the squares are 3.0625, 0.5625, 0.0625 and 5.0625.
Sum the squared deviations and divide that sum by the total quantity of numbers minus one, to calculate their average. Using the example, calculate (3.0625 + 0.5625 + 0.0625 + 5.0625) / 3 = 2.9166.
Take the square root of the calculated average. This result is the sample standard deviation. Using the example, the square root of 2.9166 is 1.708.