From a histogram I collected the following data, I'm trying to figure out
how to calculate the standard deviation of hours driving. I can do it
outside of using the stdev formula, but if I try to use the formula I mess
up my results.

Mean hrs= number of subjects/total hours driving (200/1580) = 7.9
Standard Deviation for hours driving: Needs to equal 1.05 I can get that by
taking 12702(power1580,2)/200 which = 220
taking that sum (220) and making another calculation. sqrt(220/200-1)
Those combined net the standard deviation, but there has to be an easier
way.... Any help would be appreciated.

x f xf x2f
Hours of driving Number of Subjects Total Hours driving
3.5 2 7 24.5
4.5 2 9 40.5
5.5 4 22 121
6.5 22 143 929.5
7.5 64 480 3600
8.5 90 765 6502.5
9.5 14 133 1263.5
10.5 2 21 220.5

56 199 1580 12702