It depends on the fraction
Out of a sample of 80 books, 6 were historical books. So the percentage of books in the sample will be:
%
We can use this sample to represent the entire collection of books in the library. So the best estimate of total number of historical books in the library is 7.5% of 21360 , which comes out to be:
7.5 % of 21360 =
Therefore, roughly 1602 books out of 21360 book of library are historical books.
Answer:
And rounded up we have that n=767
Step-by-step explanation:
We know the following info:
represent the sample size selected
represent the number of defectives in the sample
represent the estimated proportion of defectives
represent the margin of error desired
The margin of error for the proportion interval is given by this formula:
(a)
And on this case we have that and we are interested in order to find the value of n, if we solve n from equation (a) we got:
(b)
The crtical value for a confidence level of 95% is
And replacing into equation (b) the values from part a we got:
And rounded up we have that n=767