Question 609605
First find the mean:
{{{mu = (8 + 10 + 12 + 15 + 17 + 13)/6 = 75/6 = 12.5}}}

Then find the variance:
{{{sigma^2 = ((8 - 12.5)^2 + (10 - 12.5)^2 + (12 - 12.5)^2 + (15 - 12.5)^2 + (17 - 12.5)^2 + (13 - 12.5)^2) / 6 = ((-4.5^2) + (-2.5^2) + (-0.5^2) + (2.5^2) + (4.5^2) + (0.5^2) ) / 6 = (20.25 + 6.25 + 0.25 + 6.25 + 20.25 + 0.25) / 6 = 53.5/6 = 8.9166667}}}}

Then find the square root of the variance to get the standard deviation:
{{{sigma = sqrt(8.9166667) = 2.98608}}}