how to calculate standard deviation khan?
['The standard deviation formula may look confusing, but it will make sense after we break it down. ... ', 'Step 1: Find the mean.', 'Step 2: For each data point, find the square of its distance to the mean.', 'Step 3: Sum the values from Step 2.', 'Step 4: Divide by the number of data points.', 'Step 5: Take the square root.']