R/median.os.R

In cwendorf/dgb: DGB

# DGB
## Median from One Sample

ci.median.os <- function(alpha, y) {
 # Computes confidence interval for a population median
 # Arguments:
 #   alpha: alpha level for 1-alpha confidence
 #   y:     vector of sample scores
 # Values:
 #   median, SE, lower limit, upper limit
 n <- length(y)
 y <- sort(y)
 z <- qnorm(1 - alpha/2)
 c1 <- round((n - z*sqrt(n))/2)
 if (c1 < 1) {c1 = 1}
 median <- median(y)
 L <- y[c1]
 U <- y[n - c1 + 1]
 a <- round((n + 1)/2 - sqrt(n))
 if (a < 1) {a = 1}
 L1 <- y[a]
 U1 <- y[n - a + 1]
 p <- pbinom(a - 1, size = n, prob = .5)
 z0 <- qnorm(1 - p)
 se <- (U1 - L1)/(2*z0)
 out <- t(c(median, se, L, U))
 colnames(out) <- c("Median", "SE", "LL", "UL")
 return(out)
}