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Confidence Interval
3 messages · Rachel Keyes, Ben Bolker, rak1304
Rachel Keyes <rkeyes87 <at> hotmail.com> writes:
I am new to R and Im some trouble with the following question... Generate 100
standard normal N(0,1) samples
of size 100, X1(k),...,X100(k) where k=1,...,100 (The k is and indicie in
brackets) Calculate the sample
mean for each sample. For each sample mean Xbark the 0.95-confidence interval
for the mean mew=0 is given
by... Ik= ( Xbark plus or minus 1.96/10) Find the number of intervals such
that 0 does not belong to Ik. How
many of them do you expect to see? Well so far I have come up with... N<-100;
Nsamp<-100
A<-matrix(rnorm(N*Nsamp,0,1),ncol=Nsamp) means<-apply(A,2,mean) However I have
no idea what I am
doing and no idea if that even makes sense. Any help would be greatly
appreciated as I have no experience of
statistical software whatsoever. Thanks in Advance. Rachel
This sounds an awful lot like a homework problem. Can you convince us not by giving us a little more context? I will say that you seem to have made a pretty good start. A hint is that if you have a logical condition, sum(condition) will count the number of cases. For example, sum(means>0) will count the number of positive means. ?abs and ?">" may help too. By the way, I think that's supposed to be "mu" and not "mew". Ben Bolker
Yes it is a homework problem, I included the whole question as I thought it would make it easier to explain however I am unsure of how to do the confidence interval part. As far as I am aware I have set up a matrix with my 100 samples of 100 and have calculated means. Do I need to set up a new matrix of these means and then do a confidence interval from there? Also when I searched 'confint' in R I am confused as to how to adapt it to my problem. I am looking for the interval of each individual mean plus or minus 1.96/10 I wasnt aware of abs(x) and sum(means>0) so thankyou for pointing them out to me.
Ben Bolker wrote:
Rachel Keyes <rkeyes87 <at> hotmail.com> writes:
I am new to R and Im some trouble with the following question... Generate 100
standard normal N(0,1) samples
of size 100, X1(k),...,X100(k) where k=1,...,100 (The k is and indicie in
brackets) Calculate the sample
mean for each sample. For each sample mean Xbark the 0.95-confidence interval
for the mean mew=0 is given
by... Ik= ( Xbark plus or minus 1.96/10) Find the number of intervals such
that 0 does not belong to Ik. How
many of them do you expect to see? Well so far I have come up with... N<-100;
Nsamp<-100
A<-matrix(rnorm(N*Nsamp,0,1),ncol=Nsamp) means<-apply(A,2,mean) However I have
no idea what I am
doing and no idea if that even makes sense. Any help would be greatly
appreciated as I have no experience of
statistical software whatsoever. Thanks in Advance. Rachel
This sounds an awful lot like a homework problem. Can you convince us not by giving us a little more context? I will say that you seem to have made a pretty good start. A hint is that if you have a logical condition, sum(condition) will count the number of cases. For example, sum(means>0) will count the number of positive means. ?abs and ?">" may help too. By the way, I think that's supposed to be "mu" and not "mew". Ben Bolker
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