Mean=3061/11=278.27 (add 11 numbers together then divide by 11).
We need the mean to find the standard deviation. We find the difference between each value and the mean, then square it. The sum of the squares divided by 11 is the variance, and the square root of the variance is the standard deviation. Variance=1058/121=8.74, so standard deviation=23sqrt(2)/11=2.96.