R version 2.15.2 (2012-10-26) -- "Trick or Treat"
Copyright (C) 2012 The R Foundation for Statistical Computing
ISBN 3-900051-07-0
Platform: i686-pc-linux-gnu (32-bit)

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> par5 = '0.05'
> par4 = '0.05'
> par3 = '21'
> par2 = '20'
> par1 = '13.03'
> par1<-as.numeric(par1)
> par2<-as.numeric(par2)
> par3<-as.numeric(par3)
> par4<-as.numeric(par4)
> par5<-as.numeric(par5)
> c <- 'NA'
> csn <- abs(qnorm(par5))
> if (par2 == par3)
+ {
+ conclusion <- 'Error: the null hypothesis and alternative hypothesis must not be equal.'
+ }
> ua <- abs(qnorm(par4))
> ub <- qnorm(par5)
> c <- (par2+ua/ub*(-par3))/(1-(ua/ub))
> sqrtn <- ua*sqrt(par1)/(c - par2)
> samplesize <- sqrtn * sqrtn
> ua
[1] 1.644854
> ub
[1] -1.644854
> c
[1] 20.5
> sqrtn
[1] 11.87489
> samplesize
[1] 141.0129
> 
> #Note: the /var/wessaorg/rcomp/createtable file can be downloaded at http://www.wessa.net/cretab
> load(file="/var/wessaorg/rcomp/createtable")
> 
> a<-table.start()
> a<-table.row.start(a)
> a<-table.element(a,hyperlink('http://www.xycoon.com/ht_mean_knownvar.htm','Testing Mean with known Variance','learn more about Statistical Hypothesis Testing about the Mean when the Variance is known'),2,TRUE)
> a<-table.row.end(a)
> a<-table.row.start(a)
> a<-table.element(a,'population variance',header=TRUE)
> a<-table.element(a,par1)
> a<-table.row.end(a)
> a<-table.row.start(a)
> a<-table.element(a,'null hypothesis about mean',header=TRUE)
> a<-table.element(a,par2)
> a<-table.row.end(a)
> a<-table.row.start(a)
> a<-table.element(a,'alternative hypothesis about mean',header=TRUE)
> a<-table.element(a,par3)
> a<-table.row.end(a)
> a<-table.row.start(a)
> a<-table.element(a,'type I error',header=TRUE)
> a<-table.element(a,par4)
> a<-table.row.end(a)
> a<-table.row.start(a)
> a<-table.element(a,'type II error',header=TRUE)
> a<-table.element(a,par5)
> a<-table.row.end(a)
> a<-table.row.start(a)
> a<-table.element(a,hyperlink('http://www.xycoon.com/ht_mean_knownvar.htm#ex4','sample size','example'),header=TRUE)
> a<-table.element(a,samplesize)
> a<-table.row.end(a)
> a<-table.end(a)
> table.save(a,file="/var/wessaorg/rcomp/tmp/1nqjf1355244265.tab") 
> 
> 
> 
> proc.time()
   user  system elapsed 
  0.321   0.060   0.353