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tCImean confidence intervals for the mean

Sep 1st, 2014
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  1.    
  2.     # Hitung tCImean confidence interval
  3.     # Confidence Interval calculation, Normal distribution (Z)
  4.     #
  5.     # Sunu Pradana
  6.     # Samarinda, Indonesia, Agustus 2014
  7.     #      
  8.     # Creative Commons Attribution-ShareAlike 4.0
  9.     #
  10.     # Usage (contoh penggunaan):
  11.     # tCImean(95,10,2,5)
  12.     #
  13.     #
  14.     # CI = confidence interval (arbitrary, usually, 90, 95, or 99)
  15.     # xbar = point estimate of population mean by sample mean
  16.     # es = standard deviation of the sample
  17.     # n = Jumlah sample (sample size)
  18.     #
  19.  
  20.     tCImean <- function(CI, xbar, es, n){
  21.      
  22.     # CI ; confidence interval
  23.     # xbar ; sample point estimate mean
  24.     # es ; sample standard deviation
  25.     # n ; jumlah sample
  26.          
  27.     alpha = CI/100
  28.      
  29.     two.tail.alpha <- alpha/2
  30.     two.tail.alpha <- 1-alpha
  31.     one.tail.alpha <- two.tail.alpha/2
  32.      
  33.     left.tail.alpha <- one.tail.alpha
  34.     right.tail.alpha <- 1-one.tail.alpha
  35.      
  36.     left.t.value <- qt(left.tail.alpha, n-1)
  37.     right.t.value <- qt(right.tail.alpha, n-1)
  38.      
  39.     left.val <- xbar - ( sqrt(left.t.value^2) * ( es/sqrt(n) ) )
  40.     right.val <- xbar + ( right.t.value * ( es/sqrt(n) ) )
  41.     difr <- ( right.t.value * ( es/sqrt(n) ) )
  42.      
  43.     cat("\n")
  44.     cat( sprintf("CI, xbar, es, n" ),fill = TRUE )
  45.     cat("\n")
  46.      
  47.     cat( sprintf("%-33s %1s % 5.3f  ", "alpha", ":", alpha ),fill = TRUE )
  48.     cat( sprintf("%-33s %1s % 5.3f  ", "two.tail.alpha", ":", two.tail.alpha ),fill = TRUE )
  49.     cat( sprintf("%-33s %1s % 5.3f  ", "one.tail.alpha", ":", one.tail.alpha ),fill = TRUE )
  50.     cat("\n")
  51.     cat( sprintf("%-33s %1s % 5.6g  ", "left.t.value", ":", left.t.value          ),fill = TRUE )
  52.     cat( sprintf("%-33s %1s % 5.6g  ", "left.t.value", ":", round(left.t.value,2) ),fill = TRUE )
  53.     cat("\n")
  54.     cat( sprintf("%-33s %1s % 5.6g  ", "right.t.value", ":", right.t.value         ),fill = TRUE )
  55.     cat( sprintf("%-33s %1s % 5.6g  ", "right.t.value", ":", round(right.t.value,2)),fill = TRUE )
  56.     cat("\n")
  57.     cat( sprintf("%-33s %1s % 4.6g  ", "differ val", ":", round(difr,1)),fill = TRUE )
  58.     cat("\n")
  59.     cat( sprintf("%-33s %1s % 5.6g %12s %-5.4g %-2s ", "left.val",  ":", left.val,  "   [rounded: ", round(left.val,1), "]"  ),fill = TRUE )
  60.     cat( sprintf("%-33s %1s % 5.6g  ", "Point estimate of population mean", ":", xbar ),fill = TRUE )
  61.     cat( sprintf("%-33s %1s % 5.6g %12s %-5.4g %-2s ", "right.val", ":", right.val, "   [rounded: ", round(right.val,1),"]" ),fill = TRUE )
  62.     cat("\n")
  63.     }
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