Confidence interval for mean or median

Calculates confidence interval for the mean or median of a distribution with unknown population variance

conf.interval(x, cl = 0.95, stat = "mean", std.error = TRUE)

Arguments

x	Vector to calculate confidence interval for
cl	Percent confidence level (default = 0.95)
stat	Statistic (mean or median)
std.error	Return standard error (TRUE/FALSE)

Value

lci Lower confidence interval value

uci Upper confidence interval value

mean If stat = "mean", mean value of distribution

mean Value of the mean or median

conf.level Confidence level used for confidence interval

std.error If std.error = TRUE standard error of distribution

Author

Jeffrey S. Evans <jeffrey_evans@tnc.org>

Examples

 x <- runif(100)
 cr <- conf.interval(x, cl = 0.97) 
 print(cr)
#> $lci
#> [1] 0.4263872
#> 
#> $uci
#> [1] 0.5297245
#> 
#> $mean
#> [1] 0.4780558
#> 
#> $conf.level
#> [1] 0.97
#> 
#> $`std error`
#> [1] 0.027157
#> 

 d <- density(x)
 plot(d, type="n", main = "PDF with mean and 0.97 confidence interval")
   polygon(d, col="cyan3")
   abline(v=mean(x, na.rm = TRUE), lty = 2)
   segments( x0=cr[["lci"]], y0=mean(d$y), x1=cr[["uci"]], 
             y1=mean(d$y), lwd = 2.5, 
             col = "black")
   legend("topright", legend = c("mean", "CI"), 
          lty = c(2,1), lwd = c(1,2.5))