SAS-L,
I have a statistics question.
I understand that there are different methods for obtaining the confidence
interval for a proportion under simple random sampling. The usual method
(normal approximation) is inappropriate for small samples and for cases
with the population proportion close to 0 or 1 (in such cases the
hypergeometric distribution is to be used).
What methods are appropriate for sampling with unequal selection
probabilities (such as proportional to size sampling) and for stratified
random sampling?
From my reading of the documentation for PROC SURVEYFREQ, it looks like SAS
uses the normal approximation method. Is this appropriate if the
population proportion is close to 0 or 1? What about for small samples?
Background - The hypergeometric calculation produces a confidence interval
which is potentially asymmetric. Let H(x, n-x, A, N-A) be the
hypergeometric probability for finding in a sample of size n from a
population of size N; with x occurences in the sample and A occurences in
the population.
H(x, n-x, A, N-A) = [A choose x] * [(N-A) choose (n-x)] / [N choose n]
The upper 95% CI for the population number of occurences, A is given by
finding the smallest integer Au such that
sum from j=0 to x {H(j, n-j, Au, N-Au)}<= 0.025.
The lower limit Al for the 95% CI on population occurences is given by the
largest integer Al such that
sum from j=x to n {H(j, n-j, Al, N-Al)}<= 0.025.
The upper limit for the proportion is then Pu=Au/N, and the lower limit is
Pl=Al/N.
--Alex Cavallo
Navigant Consulting
exact confidence intervals for proportions in non-SRS setting
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- 1. data manip proc
I have a dataset with a list of dates called dates and I want to extract data for each date from check. The stored variable does not evaluate correctly. Anyone know why? Many Thanks. data dates; set dates; format alldates mmddyy10.; run; data _null_; set dates nobs=count; call symput('stored', alldates); call symput('counter', count); run; &stored; %macro GetTop30; %do i=1 %to &counter; proc sql; create table check as select * from data where date = &&stored&i; run; %.....Some extra manipulations to check............... %end; %mend; - 2. SAS Code ANCOVA baseline as covariate
I have data like this; Subject Period Sequence Formulation AUClast Pre dose value R01 1 1 S1 25.3003 1.71 R01 2 1 T2 31.6812 1.96 R01 3 1 S2 26.5744 1.72 R01 4 1 T1 28.0301 1.84 R02 1 2 S2 27.9508 1.82 R02 2 2 S1 25.528 1.61 R02 3 2 T1 21.1087 1.67 R02 4 2 T2 21.4418 1.81 R03 1 3 T1 13.7766 0.78 R03 2 3 S2 11.8601 0.78 R03 3 3 T2 11.3354 0.79 R03 4 3 S1 12.4126 0.79 R04 1 4 T2 20.071 1.49 R04 2 4 T1 15.1978 1.27 R04 3 4 S1 19.6033 1.52 R04 4 4 S2 16.9579 1.29 R05 1 4 T2 22.3924 1.7 R05 2 4 T1 22.1381 1.61 R05 3 4 S1 23.0792 1.82 R05 4 4 S2 25.7839 1.74 What will be the SAS code for ANCOVA to be run using baseline as covariate on data for comparing test low dose (T1) vs ref. Low (s1) dose and also test high dose (T2) vs ref. high dose (S2) and calculate the 95% CI for these comparisons. Thanks in advance AM - 3. SAS 8.2 AF Build (Source) Window: How to Persist Window Size
Kevin, I don't have access to 8.2, but I just tested this with 9.2 Phase 2. I suspect it was the same for 8.2. You can use the SAS Registry Editor to change the values for Height, Width, HorizontalPosition, VerticalPosition: Products->AF->Design Time->Source Window It works for both the original source editor and the Enhanced Editor. -Randy -----Original Message----- From: SAS(r) Discussion [mailto: XXXX@XXXXX.COM ] On Behalf Of Kevin Myers Sent: Tuesday, July 28, 2009 3:01 PM To: XXXX@XXXXX.COM Subject: SAS 8.2 AF Build (Source) Window: How to Persist Window Size and Position Under MS Windows? Can someone please remind me how to persist the size and position of the SAS/AF Build window (source editor) when running SAS 8.2 under MS Windows? I'm pretty sure that I used to do that years ago when I was programming full time, but now it has slipped my mind and I can't seem to locate that info in the docs. I know that the WSAVE command does NOT work for this window... Thanks, Kevin M.
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exact confidence intervals for proportions in non-SRS setting
by acavallo » Wed, 18 May 2005 14:19:58 GMT
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