# R-program for Supplementary Exercise 6.95 of IPS7e
# see R-program for 6.13 for more details about the commands

detect <- read.csv("h:/vhm/vhm801/Datasets/csv/Chapter 6/ex06_095.csv")

# write a function to do the calculation
z.ci = function(a, sd, conf.level=0.95){
   lower = mean(a) - qnorm(1-(1-conf.level)/2)*sd/sqrt(length(a))
   upper = mean(a) + qnorm(1-(1-conf.level)/2)*sd/sqrt(length(a))
   return(as.vector(c(lower,upper)))
}
z.ci(detect$radon, sd=9, conf.level=0.95)

# use add-on library TeachingDemos
library(TeachingDemos)
z.test(detect$radon, mu=105, sd=9, conf.level=0.95)