Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down at the end of May, and its replacement, statalist.org is already up and running.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: random allocation three-way cross-over design


From   Steve Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: random allocation three-way cross-over design
Date   Sat, 1 May 2010 14:19:31 -0400

There is an -ntreat()- option in -ralloc- and ntreat(3) is legal.
However -ralloc- is intended to allocate different subjects to
treatments in randomized clinical trials, not cross-over studies. DR
Cox, 1958, Planning of Experiments, Wiley, page 271, states that, if
there are no carry-over effects, the appropriate design is a 3 x 3
Latin square in which each treatment occurs equally often in each
period and each subject. When there are carry-over effects, the design
should also ensure that "each treatment follows each other treatment
the same number of times" (p. 273). I am sure that there is a more
recent literature on cross-over designs, and I suggest that you
consult it.

Steve


On Sat, May 1, 2010 at 11:42 AM, Stas Kolenikov <skolenik@gmail.com> wrote:
> On Sat, May 1, 2010 at 8:30 AM, Hadewijch Vandenheede
> <hvdheede@vub.ac.be> wrote:
>> I wish to generate a randomization scheme for a 3-way cross-over study with
>> three treatments.
>>
>> I'm trying to establish such scheme with 'ralloc' but it doesn't seem to
>> work out, because it can only handle 2-way cross-over designs.
>>
>> Is there another way of doing this?
>
> I know very little about experiment design (although I took a couple
> of classes back in grad school 10 years ago), but I imagine that if
> you can get the complete design matrix, you can permute its rows and
> randomly assign your experimental units to these rows.
>
> --
> Stas Kolenikov, also found at http://stas.kolenikov.name
> Small print: I use this email account for mailing lists only.
> *
> *   For searches and help try:
> *   http://www.stata.com/help.cgi?search
> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/
>



-- 
Steven Samuels
sjsamuels@gmail.com
18 Cantine's Island
Saugerties NY 12477
USA
Voice: 845-246-0774
Fax: 206-202-4783

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/


© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   Site index