R/mean_test2.R

In OneTwoSamples: Deal with One and Two (Normal) Samples

mean_test2<-function(x, y, 
   sigma=c(-1, -1), var.equal=FALSE, side=0){
   ## source("p_value.R")
   n1<-length(x); n2<-length(y)
   xb<-mean(x); yb<-mean(y)
   if (all(sigma>=0)){
      z<-(xb-yb)/sqrt(sigma[1]^2/n1+sigma[2]^2/n2)
      P<-p_value(pnorm, z, side=side)
      data.frame(mean=xb-yb, df=n1+n2, Z=z, p_value=P)
   }
   else{
      if (var.equal ==  TRUE){
         Sw<-sqrt(((n1-1)*var(x)+(n2-1)*var(y))/(n1+n2-2))
         t<-(xb-yb)/(Sw*sqrt(1/n1+1/n2))
         nu<-n1+n2-2
      }
      else{
         S1<-var(x); S2<-var(y)
         nu<-(S1/n1+S2/n2)^2/(S1^2/n1^2/(n1-1)+S2^2/n2^2/(n2-1))
         t<-(xb-yb)/sqrt(S1/n1+S2/n2)
      }
      P<-p_value(pt, t, paramet=nu, side=side)
      data.frame(mean=xb-yb, df=nu, T=t, p_value=P)
   }
}