### Example1(Jackknife estimate of bias) data(patch, package = "bootstrap")
n <- nrow(patch)
y <- patch$y
z <- patch$z
theta.hat <- mean(y) / mean(z)
print (theta.hat)
#compute the jackknife replicates, leave-one-out estimates
theta.jack <- numeric(n)
for (i in 1:n)
theta.jack <- mean(y[-i]) / mean(z[-i])
bias <- (n - 1) * (mean(theta.jack) - theta.hat)
print(bias) #jackknife estimate of bias
### Example2 (Jackknife estimate of standard error)
se <- sqrt((n-1) * mean((theta.jack - mean(theta.jack))^2))
print(se)
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