Mô hình Bayes cho sự khác biệt giữa 2 tỉ lệ

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#Bai viet mo phong lai code va video cua GS Nguyen Van Tuan - ## link video: https://www.youtube.com/watch?v=Yz-evMBOUsI

#data
x1=652; n1=10343
x2=1473; n2=20173

#prior
alpha1=1; beta1=1
alpha2=1; beta2=1

#posterior

p1=rbeta(100000, x1+alpha1, n1-x1+beta1)
p2=rbeta(100000, x2+alpha2, n2-x2+beta2)
head(p1)

## [1] 0.06843026 0.06198538 0.06232521 0.06302281 0.05880406 0.06416481

head(p2)

## [1] 0.07120820 0.07068447 0.07353819 0.07259753 0.07290238 0.07527757

diff=p1-p2

plot(density(diff), main="posterior distribution of diff")

quantile(diff, c(0.025, 0.5, 0.975))

##         2.5%          50%        97.5% 
## -0.015801987 -0.009945238 -0.004018315