Reorganized the folders and started a common script for the lectures.

bootstrap/code/bootstrapsem.m

@@ -0,0 +1,24 @@
+nsamples = 100;
+nresamples = 1000;
+
+% draw a SRS (simple random sample, "Stichprobe") from the population:
+x = randn( 1, nsamples );
+fprintf('%-30s  %-5s  %-5s  %-5s\n', '', 'mean', 'stdev', 'sem' )
+fprintf('%30s  %5.2f  %5.2f  %5.2f\n', 'single SRS', mean( x ), std( x ), std( x )/sqrt(nsamples) )
+
+% bootstrap the mean:
+mus = zeros(nresamples,1);  % vector for storing the means
+for i = 1:nresamples        % loop for generating the bootstraps
+    inx = randi(nsamples, 1, nsamples);  % range, 1D-vector, number
+    xr = x(inx);            % resample the original SRS
+    mus(i) = mean(xr);      % compute statistic of the resampled SRS
+end
+fprintf('%30s  %5.2f  %5.2f  -\n', 'bootstrapped distribution', mean( mus ), std( mus ) )
+
+% many SRS (we can do that with the random number generator, but not in real life!):
+musrs = zeros(nresamples,1);      % vector for the means of each SRS
+for i = 1:nresamples
+    x = randn( 1, nsamples );     % draw a new SRS
+    musrs(i) = mean( x );         % compute its mean
+end
+fprintf('%30s  %5.2f  %5.2f  -\n', 'sampling distribution', mean( musrs ), std( musrs ) )