Midterm Review

Can anyone point me in the right direction for finding the standard deviation on problem 12 ©?

sqrt(((x_1-m)^2+(x_2-m)^2+(x_3-m)^2+(x_4-m)^2)/(n-1))

For our problem x_1=1.05, x_2=1.15, x_3=1.2, x_4=1.1. The mean was previously stated as m=1.125 and n=4

After putting that information in, our equation looks like this:

sqrt(((1.05-1.125)^2+(1.15-1.125)^2+(1.2-1.125)^2+(1.1-1.125)^2)/(4-1))