Bioequivalence and Bioavailability Forum • Intrasubject CV from CI with power to R

Intrasubject CV from CI with power to R [Power / Sample Size]

posted by d_labes – Berlin, Germany, 2010-11-25 11:11 (5321 d 21:49 ago) – Posting: # 6218
Views: 7,744

Dear Earlybird, dear All,

for those who have access to R and have installed the package PowerTOST here an add-on function:

require(PowerTOST)

CVfromCI <- function(point,lower,upper,n,design="2x2",alpha=0.05)

{

  if (missing(lower) | missing(upper)) stop("Lower and upper CL must be given!")

  if (missing(n)) stop("Sample size must be given!")

  

  if (missing(point)) point <- sqrt(lower*upper) 

  

  # get design characteristics

  d.no <- .design.no(design)

  if (is.na(d.no)) stop("Unknown design!")

  desi <- .design.props(d.no)

  dfe  <- parse(text=desi$df[1],srcfile=NULL) #degrees of freedom as expression



  tval <- qt(1-alpha,eval(dfe))

  s1 <- (log(point)-log(lower))/sqrt(desi$bk/n)/tval

  s2 <- (log(upper)-log(point))/sqrt(desi$bk/n)/tval

  sw <- 0.5*(s1+s2)

  # both estimates very different?

  if (abs(s1-s2)/sw>0.1) warning("sw1, sw2 very different. Check input.")

  return(se2CV(sw))

}

With this function you can obtain the CV from each design :cool:

known within PowerTOST.
This function will be included in the next release of PowerTOST if the author of that package will accept the code :-D

. Any enhancement or comment welcome.

Taking the numbers from the first post in this thread and assuming 24 subjects one gets:

CVfromCI(point=1.03,lower=0.93,upper=1.15,n=24,design="2x4x4")

[1] 0.3196356

i.e. CV=32%.

—
Regards,

Detlew

Complete thread:

Intrasubject CV from replicate design earlybird 2010-11-24 16:34 [Power / Sample Size]
- Intrasubject CV from replicate design Helmut 2010-11-24 18:47
  - Intrasubject CV from replicate design earlybird 2010-11-25 07:58
    - Boss button Helmut 2010-11-25 13:54
      - Boss button earlybird 2010-11-26 10:20
- Intrasubject CV from 2x4x4 replicate crossover d_labes 2010-11-25 08:19
  - Intrasubject CV from 2x4x4 replicate crossover earlybird 2010-11-25 11:08
- Intrasubject CV from CI with power to Rd_labes 2010-11-25 10:11
  - Bravo! Helmut 2010-11-25 14:08
    - Bravo ... oh! d_labes 2010-11-25 14:47
      - PowerTOST for R Helmut 2010-12-23 03:42