Quote:
Originally Posted by Fozzie_DeBear
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...  ) |
the sample standard deviation is represented within the 1.98% range provided and i think your right on the sample mean but you can use population proportion(p(hat)) instead if sample mean isn't known. At least one of my examples in class did.
So assuming my first example is right, heres the results for round 2
a) first we need to find p(hat)=262/746=0.3512=35.12% 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=0.3512 +/- 1.96 (0.0198)
p=0.3512 +/- 0.0388
p=0.3124, 0.3900
so what that means is that you are correct 95%(19 times out of 20) that your data falls within the range of 31.24%(227) and 39.00%(291) if you have a standard error of 1.98%