Finding variance without knowing mean?

[MadMike1986]

Hi,

my girlfriend is taking a business statistics class and she had a test today. she got stumped on a question and wrote it down so she could ask me about it when she got back since I'm pretty good at math. I tried solving it but from what i can tell it seems like you would need to know the mean in order to find the variance. the question is below:

Find the Variance:

n = 5
$$\Sigma x^{2}$$ = 1320
$$\Sigma$$x = 80


I expanded out the variance formula. since we run from i=1 to n (where n=5)
I got the formula V = 1320 - 160$$u^{2}$$ + 5$$u^{2}$$$$/5$$

where u = the mean.

My girlfriend says that the mean was not specified in the problem. I would have given my answer for the variance as a function of the mean as you can see above, but since this is a business statistics class i have the tendency to believe the teacher is expecting a numerical answer. Does anyone have any insight into how this problem can be solved, or is there not enough information given?

Thank you.

 

[MadMike1986]

note: in the variance formula that i expanded out, i meant for the entire numerator to be divided by 5. (n=5)

 

[MadMike1986]

crap i just realized that i wasn't supposed to post this under here. i would delete it but i haven't figured out how yet. until i do i apologize.