Bootstrape case-resampling Logistic regression

mihhghjl — Fri, 22 Jul 2022 20:12:52 GMT

I am trying to do logistic regression bootstrap case resampling on my data which contains sample size of 71. Case/control study with four binary independent variables. I have the following code and output but unsure about two things.

- Do I need to have "freq NumberHits" in step 3 if I use "outhits" in step 2? I am unsure what the freq step does in the logistic regression.

- Is the output for the 95% CI the Estimated Coefficients which I would then exponentiate to obtain the odds ratio interval?

/* 1. compute the statistics on the original data */

proc logistic data=cwd.final3;
class s8a1yn(ref='1') '28cat01'n(ref='1') '23cyn'n(ref='1') dist_wild_10kmyn(ref='1') / param=reference;
model casenum= '23cyn'n '28cat01'n s8a1yn dist_wild_10kmyn / firth covb; /* original estimates */
run;
quit;

title "Bootstrap Distribution of Estimates";
title2 "Case Resampling";
%let NumSamples = 10000; /* number of bootstrap resamples */
%let IntEst = -3.5228; /* intercept estimate under analysis of max likelihood original estimates for later visualization */
%let Est23 = 1.5088;
%let Est28 = 1.7238;
%let Estdist = 1.6265;
%let Estimp = 2.2814;

/* 2. Generate many bootstrap samples by using PROC SURVEYSELECT */
proc surveyselect data=sample seed=1234
out=BootCases(rename=(Replicate=SampleID))
method=urs /* resample with replacement */
sampsize=71 /* each bootstrap sample has N observations */
outhits /* OUTHITS use OUTHITS option to suppress the frequency var */
reps=&NumSamples; /* generate NumSamples bootstrap resamples */
run;

/* 3. Compute the statistic for each bootstrap sample */
proc logistic data=BootCases outest=PEBoot noprint;
by sampleID;
freq NumberHits;
class '23cyn'n(ref='1') '28cat01'n(ref='1') s8a1yn(ref='1') dist_wild_10kmyn(ref='1') / param=reference;
model casenum= '23cyn'n '28cat01'n s8a1yn dist_wild_10kmyn / firth covb;
run;
quit;

/* 4. Obtain the 95% CI*/

proc stdize data=PEBoot vardef=N pctlpts=2.5 97.5 PctlMtd=ORD_STAT outstat=Pctls;
var Intercept '23cyn0'n '28cat010'n s8a1yn0 dist_wild_10kmyn0;
run;

proc report data=Pctls nowd;
where _type_ =: 'P';
label _type_ = 'Confidence Limit';
columns ('Bootstrap Confidence Intervals of Estimated coefficients(B=10,000)' _ALL_);
run;

Re: Bootstrape case-resampling Logistic regression

sbxkoenk — Fri, 22 Jul 2022 23:36:27 GMT

Look here :

Bootstrap regression estimates: Case resampling
By Rick Wicklin on The DO Loop October 24, 2018
https://blogs.sas.com/content/iml/2018/10/24/bootstrap-regression-case-resampling.html

Koen

Re: Bootstrape case-resampling Logistic regression

mihhghjl — Sat, 23 Jul 2022 18:48:03 GMT

That is where I got my code from but I could find the answers to my questions in that article (unless I missed them).

topic Re: Bootstrape case-resampling Logistic regression in SAS Software for Learning Community

Bootstrape case-resampling Logistic regression

Re: Bootstrape case-resampling Logistic regression

Re: Bootstrape case-resampling Logistic regression