1. Choosing sample size

Hello. I am not sure about the complexity of the question I'm asking but its nothing like what I did in high school so I hope this is the correct forum.

I have sets of 300 integers whose value can range between 330 and 370. The mean comes out to be in the range of 350-360 with a CV in the range of 1%.

Because these values are discovered through destructive testing, a small sample size is preferred. I want to know how to quantify the relationship between the sample size and the expected deviation from the mean/cv of the entire population. Any pointers in the right direction or what additional parameters are required would be great.

2. Hi there, are you aware of that the confidence interval for the mean at $\displaystyle (1-\alpha)$ % is $\displaystyle \bar{x}\pm t_{\alpha , n-1 }\times \frac{s}{\sqrt{n}}$ ?

3. Hello, I think a key piece of information I left out is that standard deviation of these sets varies and I'm equally interested in the relation between sample size and observed/population cv. Is it valid to work out the mean and standard deviation of resulting CVs to do this? How would this relate back to the sample size?