The correct answer is: $\sqrt{33}\approx5.7446$
Explanation
We compute the population standard deviation of the ten numbers. First find the mean, then the sum of squared deviations, then the variance and square root.
Steps:
- Mean:
$$\bar{x}=\frac{2+4+6+\cdots+20}{10}=\frac{110}{10}=11$$
- Sum of squared deviations:
$$\sum_{i=1}^{10}(x_i-\bar{x})^2=81+49+25+9+1+1+9+25+49+81=330$$
- Variance (population):
$$\sigma^2=\frac{1}{10}\sum_{i=1}^{10}(x_i-\bar{x})^2=\frac{330}{10}=33$$
- Standard deviation:
$$\sigma=\sqrt{33}\approx5.7446$$
Therefore the standard deviation is $\sqrt{33}\approx5.7446$. (If you wanted the sample standard deviation, use denominator $n-1=9$, which gives $\sqrt{330/9}\approx6.0553$.)