R/tt2st.R

In EQUIVNONINF: Testing for Equivalence and Noninferiority

tt2st <- function(m,n,alpha,eps1,eps2,tol,itmax) {

ny <- m + n - 2
del1 <- -eps1*sqrt(m*n/(m+n))
del2 <- eps2*sqrt(m*n/(m+n))
err1 <- -alpha
c1 <- (del1+del2) / 2

err2 <- NA
S8 <- 0

while (err1 < 0)
     { c1 <- c1 - 0.05
       areac1_2 <- pt(c1,ny,del2)
       if (is.na(areac1_2))
         { S8 <- 1
           break }
       h <- alpha + areac1_2
       c2 <- qt(h,ny,del2)
       err1 <- pt(c2,ny,del1) - pt(c1,ny,del1) - alpha
     }

if (S8 == 0)
  { c1l <- c1
    c1r <- c1 + 0.05
    it <- 0
    while (abs(err1) >= tol && it <= itmax)
         { it <- it + 1
           c1 <- (c1l+c1r) / 2
           h <- alpha + pt(c1,ny,del2)
           c2 <- qt(h,ny,del2)
           err1 <- pt(c2,ny,del1) - pt(c1,ny,del1) - alpha
           if (err1 <= 0)
              c1r <- c1   else
              c1l <- c1
          }
  }

if (S8 == 1)
  { c2 <- qt(alpha,ny,del2)
    c1 <- qt(1-alpha,ny,del1)
    areac1_1 <- pt(c1,ny,del1)
    areac2_1 <- pt(c2,ny,del1)
    if (is.na(areac2_1)) areac2_1 <- 1
    err1 <- areac2_1 - areac1_1 - alpha
    areac1_2 <- pt(c1,ny,del2)
    areac2_2 <- pt(c2,ny,del2)
    if (is.na(areac1_2)) areac1_2 <- 0
    err2 <- areac2_2 - areac1_2 - alpha
  }

pow0 <- pt(c2,ny) - pt(c1,ny)

cat("  m =",m,"  n =",n," alpha =",alpha,"  eps1 =",eps1,
    "  eps2 =",eps2,"  it =",it,"  c1 =",c1,"  c2 =",c2,"  ERR1 =",err1,
    "  ERR2 =",err2,"  POW0 =",pow0)
}