inst/snippet/binom-odds-ci.R

In fastR2: Foundations and Applications of Statistics Using R (2nd Edition)

loglik.binom2 <- function(theta, x, n) {
  x * log(theta / (1 + theta)) + (n - x) * log(1 / (1 + theta))
}
ml.binom2 <- maxLik2(loglik.binom2, start = (odds = 1), x = 35, n = 55)
coef(ml.binom2)
x <- 35; n <- 55; theta.hat <- 35 / 20; theta.hat
pval_minus_critical2 <- function(theta0) {
    2 * (loglik.binom2(theta.hat, x, n) - loglik.binom2(theta0, x, n)) - 
    qchisq(.95, df = 1)
  } 
lo2 <- 
  uniroot(pval_minus_critical2, c(0, theta.hat)) %>% value()
hi2 <- 
  uniroot(pval_minus_critical2, c(theta.hat, 100)) %>% value()

c(lo2, hi2)
c(lo2, hi2) / (1 + c(lo2, hi2))
c(lo, hi)    # interval computed previously, for comparison