Question: how to calculate standard deviation of two samples?
Answer: Step 1: Calculate the mean of the data—this is xˉx, with, \bar, on top in the formula.
Step 2: Subtract the mean from each data point. ... 
Step 3: Square each deviation to make it positive.
Step 4: Add the squared deviations together.
Step 5: Divide the sum by one less than the number of data points in the sample.