N=200000 bwt=rnorm(N,2100,700) lowbwt=ifelse(bwt<1500,1,0) barplot(table(lowbwt)) p=sum(lowbwt)/N p n=300 # Simulando várias amostras de tamanho n nsim=1000 pchapeu=NULL ep=NULL for (i in 1:nsim){ amostra=sample(lowbwt,size=n,replace=TRUE) pchapeu=c(pchapeu,mean(amostra)) ep=c(ep,sqrt(mean(amostra)*(1-mean(amostra))/n)) } hist(pchapeu,prob=TRUE,xlab='Prop. amostral de bebês com peso<1500g',main='') lines(seq(0,1,l=100),dnorm(seq(0,1,l=100),p,sqrt(p*(1-p)/n))) sd(pchapeu) sqrt(p*(1-p)/n) sqrt(mean(pchapeu)*(1-mean(pchapeu))/n) #IC de aproximadamente 95% para p li=pchapeu-z*ep ls=pchapeu+z*ep #probabilidade de cobertura pc=sum(ls>p&lip&li