what is meant by Confidence Interval and how on can calculate it?

Question

listen my population size is about 9000 and i want a representative sample from that i am confuse how much should i drawn. So i reffer to http://www.researchinfo.com/docs/calculators/samplesize.cfm
but now my problem is what is my Confidence Interval. Can anybody help me Please.

Answer 1

Page 2 of 7 on this website shows an example of
An Estimation of a Population Proportion. I would copy it but it won't let me. Click here;
http://vc.bc.ca/~cfreire/math/Math%2012%20Solutions%20PDF%20File/Chapter%208%20Solutions%20PDF/Math12%208-8%20Solutions.pdf

I also found this information on this website;
http://en.wikipedia.org/wiki/Confidence_interval

In statistics, a confidence interval (CI) for a population parameter is an interval between two numbers with an associated probability p which is generated from a random sample of an underlying population, such that if the sampling was repeated numerous times and the confidence interval recalculated from each sample according to the same method, a proportion p of the confidence intervals would contain the population parameter in question. Confidence intervals are the most prevalent form of interval estimation.

It must be noted that a confidence interval is not in general equivalent to a (Bayesian) credible interval. The common error of equating the two is known as the prosecutor's fallacy.

If U and V are statistics (i.e., observable random variables) whose probability distribution depends on some unobservable parameter θ, and
Pr (U < 0 < V \ 0) = x
(where x is a number between 0 and 1)
then the random interval (U, V) is a "(100·x)% confidence interval for θ". The number x (or 100·x%) is called the confidence level or confidence coefficient. In modern applied practice, most confidence intervals are stated at the 95% level (Zar 1984).

There is also this website that might help you;
http://www.medbib.com/Confidence_interval