regr.est <- function(x, y, mux, N = NA)
{
# regression estimator of a population mean and total.
# x is auxiliary variable, y is response, mux is population mean
# of x, N is population size (assumed
# infinite if no value given), 
	if(length(x) != length(y)) stop("x and y must be same length")
	n <- length(x)
	fpc <- 1
	if(!is.na(N))
		fpc <- (N - n)/N
	ab <- lsfit(x, y)
	cat("mu-hat=", ab$coef[1] + ab$coef[2] * mux, "  SE=", sqrt((fpc *
            sum(ab$residual^2))/(n * (n -2))), "\n")
	if(!is.na(N))
	cat("tau-hat=", N*(ab$coef[1] + ab$coef[2] * mux), "  SE=", N*sqrt((fpc *
            sum(ab$residual^2))/(n * (n -2))), "\n")
}