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@@ -278,69 +278,3 @@
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#+end_src
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#+end_src
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** Introduction to the t distribution :ignore:
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#+RESULTS: sampling4
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[[file:bsample4.png]]
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#+NAME: sampling4
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#+BEGIN_SRC R :results output graphics :exports results :file bsample4.png :width 2500 :height 2000 :res 300
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library(data.table)
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library(ggplot2)
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options(scipen=9999)
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readRDS("plfsdata/plfsacjdata.rds")->worker
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worker$standardwage->worker$wage
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c(1:nrow(worker))->worker$SamplingFrameOrder
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worker[sex!=3,]->worker
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worker->t9
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(t9$wage-mean(t9$wage))/sqrt(var(t9$wage))->t9$wage
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ggplot(t9,aes(wage))+geom_density(colour="black",size=1)->p
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p+scale_y_continuous(limits=c(0,0.75))->p
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p+scale_x_continuous(limits=c(-15,15)
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,breaks=c(-15,0,round(mean(worker$wage)),15))->p
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p+theme_bw()->p
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p
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data.frame(sno=c(),meancol=c(),sterr=c())->t4
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samplesize=50
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for (i in c(1:20000)) {
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sample(1:nrow(worker),samplesize, replace=FALSE)->a1
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worker[a1,]->s1
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rbind(t4,data.frame(
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sno=i,
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meancol=mean(s1$wage),
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sterr=sqrt(var(s1$wage))/sqrt(samplesize)))->t4
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}
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(t4$meancol-mean(t4$meancol))/t4$sterr->t4$teststat
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(t4$meancol-mean(t4$meancol))/sqrt(var(t4$meancol))->t4$teststat2
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data.frame(modelt=rt(20000,29))->m
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var(t4$teststat)
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var(m$modelt)
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var(t4$teststat2)
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ggplot()->p
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p+geom_density(data=t4,aes(teststat),colour="blue",size=1)-> p
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p+geom_density(data=m,aes(modelt),colour="darkolivegreen",size=1)->p
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p+geom_density(data=t4,aes(teststat2),colour="red",size=1)-> p
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p+annotate("text",x=3,y=0.4,
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label=paste("Var of statistic with unknown variance:",
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round(var(t4$teststat),2)),
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colour="blue")->p
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p+annotate("text",x=3,y=0.39,
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label=paste("Var of statistic with known variance:",
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round(var(t4$teststat2),2)),
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colour="red")->p
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p+annotate("text",x=3,y=0.38,
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label=paste("Var of t-distribution:",round(var(m$modelt),2)),
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colour="darkolivegreen")->p
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p
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#+end_src
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