
Standard deviation
I'm sorry if I posted in the wrong section. (If I did tell me what section it's supposed to go) Anyways, how do I find the standard deviation of something when I only know the average and the amount of "tests" there were.
Like take this question for example: 300 equal samples were taken from a lake. 225 of the samples were in the pH range from 5.5 to 6.5. The mean pH is 6.0. What is the standard deviation?
Also, if there happens to be a way, let me know if I can somehow do this on a calculator program (TI83 Plus).
Thank you.

Do you have the data?
Sample standard deviation:
$\displaystyle s= \sqrt{\frac{1}{n1}\sum(x_i  \mu)^2}$