Question 1077781: 9.2 #16
People were polled on how many books they read the previous year. Initial survey results indicate that s=17.7 books. Complete parts (a) through (d) below.
a) How many subjects are needed to estimate the mean number of books read the previous year within four books with 95% confidence?
b) How many subjects are needed to estimate the mean number of books read the previous year within 2 books with 95% confidence?
this confidence level requites how many subjects?
c) how many subjects are needed to estimate the mean number of books read the previous year within four books with 9% confidence?
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! interval is 1.96*s/sqrt(n). I will use z, as I suspect n is large. If not, I will iterate with t.
1.96*17.7/sqrt(n)=4
n=75.22 when squaring and rearranging.
Will use t=2
[2*17.7/4]^2=78.32 or 79.
This has a t=1.99
n=78
with 2 books, this will be a much higher sample size
313.29, round to 314, and z is used here.
For the last, I am going to assume 99% is meant.
use 2.576 for z
129.93 or 130 books.
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