Calculate mean and standard deviation of a series excluding two variable?

Let me assume the the max and min values are evenly distributed around the mean. Since the range is six, the max is 12 and the min is 6.

- Removing these two values will not change the mean, the so new mean is still 9.

- The formula for std deviation is sqrt( sum^2(deviations from the mean) / (n-1) ). So if the std dev = 2 then the std deviation^2 = 4. 4 (n-1) = 44 = sum^2(deviations from the mean).

- The two values you removed each had a deviation of three from the mean. Removing 3^2 from 44 twice leaves you with 26

- Running the formula forward you now have std dev = sqrt ( 26 / 9) = 1.7lbs