# Thread: Sample Random Sample Question 2

1. ## Sample Random Sample Question 2

A Sample of size n drawn at random without replacement from a population of size N, indicated that r have a certain characteristic.

a) Derive the variance r.
b) Write down the 95% confidence interval for p.

Im not sure what Dervice the varinace of r mean?

or im not sure about part b?

Im just uset with numbers and i cant seem to get my head around this one.

2. Originally Posted by morrybo
A Sample of size n drawn at random without replacement from a population of size N, indicated that r have a certain characteristic.

a) Derive the variance r.
b) Write down the 95% confidence interval for p.

Im not sure what Dervice the varinace of r mean?

or im not sure about part b?

Im just uset with numbers and i cant seem to get my head around this one.
My post here may help you in regards to confidence intervals: http://www.mathhelpforum.com/math-he...-question.html

What is the special characteristic of the subset r? With no information present, I do not see how we can find the variance??

3. Sorry im just going by my college exam papers.

Heres another example of a question similar to the first one i posted.

To Estimate the average income in a certain area, a simple random of size n is chosen without replacement from the population of size N.

a) Derive the variance of the estimator.

b) Obtain a 95% confidence interval for the Y(bar).