Quote:
Originally Posted by CrispyGriz
So, if I'm on the right track, what you are looking for is a confidence interval based off the data you have provided.
a) first we need to find p(hat)=396/1600=0.2475=24.75% of the households
b) to find a 95%confidence interval we know
1-alpha=0.95
alpha=.05
alpha/2=.025
z*=1.96(using a z table)
Standard Error(SE)=1.98% or 0.0198
p=p(hat) +/- z* (SE)
p=0.2475 +/- 1.96 (0.0198)
p=0.2475 +/- 0.0388
p=0.2087,0.2863
so what that means is that you are correct 95%(19 times out of 20) that your data falls within the range of 20.87%(334) and 28.63%(459) if you have a standard error of 1.98%
I'm pretty sure this is what you need. If someone could verify that I'm right it might be a good thing because i just learned this stuff today so i may have a dumb mistake somewhere in it.
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I am relearning this stuff now for the CFA level 1...I think that there is a problem though...the 396/1600 is the sample/population which you don't really need (aside from reassuring yourself that you have a sufficiently large sample to represent the population).
To get a real confidence interval we need to know the sample mean and the sample standard deviation...I think...
(I also think if I don't study more I am doomed...
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