How to get the probability from the mean of a random variable?

[EGD Eric]

Homework Statement

From past experience, a professor knows that the test score of students taking a final examination is a random variable with mean 65.

Give an upper bound on the probability that a student's test score will exceed 75.

Homework Equations

None that I know of.

The Attempt at a Solution

I tried seeing if I could get the standard deviation, in the hopes that I could do something with that, but I don't know how to even get the variance.

I've tried looking at this problem from a bunch of different angles, writing it out, etc.. I'm seriously stuck! Any help or hints would be greatly appreciated!

 

[adoado]

Is this normally distributed?

 

[EGD Eric]

I think so.