Standard deviation

#1
Hello,
I have my final exam on wednesday so i am revising standard deviation from the CGP revision guide.

I have tried there example and many others and i can get it to work though the question provided contains negative numbers and i cannot get the same result as the answer page or online calculators. I am doing it this way...

Find the variance and standard deviation of these numbers:
-1 4 -2 5 3 2 2 1 0 1

n = 10
mean = 1.5
mean squared = 2.25

x x2
-1 -1
4 16
-2 -4
5 25
3 9
2 4
2 4
1 1
0 0
1 1

Total : 55

Variance = (55/10)-2.25 = 3.25

The answer book shows 4.25

Where am i going wrong....

Thanks
Ben :)