Bioequivalence and Bioavailability Forum • probability nearly zero!

probability nearly zero! [Regulatives / Guidelines]

posted by Helmut – Vienna, Austria, 2012-06-16 19:08 (5113 d 05:53 ago) – Posting: # 8761
Views: 15,238

Dear Detlew!

❝ ❝ The randomization (by chance) was:

❝ ❝ RT TR RT TR RT TR RT TR RT TR RT TR (12 runs)

❝

❝ Wow! What is the probability to obtain this by chance?

~1:500 (including the reverse order); try it yourself:

set.seed(16062012)

size       <- 12

sims       <- 1e7

y          <- rep(c(-1,1), size/2)

z          <- rep(c(1,-1), size/2)

alternate  <- 0

for (i in 1:sims) {

  x <- 1

  while (sum(x) != 0) x <- sign(rnorm(size))

  if (all(x == y) | all(x == z)) alternate <- alternate+1

}

cat(paste("‘alternating’ runs:", format(100*alternate/sims, digits=15), "%\n"))

“Nine nine nine nine nine nine” wouldn’t pass the algo, since not balanced. :-D

❝ BTW: My randomisation approach was always to randomize by blocks (block size 4 or if not possible by 2). Never obtained such an 'extreme' randomlist.

Chance for block size 4 ~0.9% and for block size 2 ~3%. ;-)

❝ Random freaks may use varying block sizes chosen at random.

Too stupid to code that…

—
Dif-tor heh smusma 🖖🏼 Довге життя Україна!
Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. 🚮
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Complete thread:

USFDA requirement for randomization Ravi 2012-06-15 13:39 [Regulatives / Guidelines]
- randomization: validation Helmut 2012-06-15 17:39
  - randomization: runs test? validation? d_labes 2012-06-16 13:10
    - randomization: runs test? validation? Helmut 2012-06-16 14:00
      - probability nearly zero? d_labes 2012-06-16 16:11
        
        probability nearly zero!Helmut 2012-06-16 17:08
        
        R-package randomizeBE d_labes 2012-07-06 09:54
        
        R-package randomizeBE Helmut 2012-07-06 12:51
  - randomization: validation ElMaestro 2012-06-16 13:31
    - randomization: runs test Helmut 2012-06-16 14:42
      - randomization: runs test ElMaestro 2012-06-16 14:48
        
        randomization: runs test Helmut 2012-06-16 15:10
      - very cool coding style ElMaestro 2012-06-16 19:12
        
        Better a good steal than a bad reinvention Helmut 2012-06-17 13:22
        
        Better a good steal than a bad reinvention ElMaestro 2012-06-17 19:58
        
        Sorry! Helmut 2012-06-18 13:26
        
        Sorry! ElMaestro 2012-06-18 15:19
        
        Dancing with the dice d_labes 2012-06-18 15:38
        
        Silly's randomization 2x2 xover d_labes 2012-06-18 16:30
        
        Silly's randomization 2x2 xover Helmut 2012-06-18 17:14
        
        Clumsy code Helmut 2012-06-18 17:42
        
        Clumsy code ElMaestro 2012-06-18 18:01
        
        Speed kills Helmut 2012-06-18 18:56
        
        Speed kills jag009 2012-09-17 21:46