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RegisterSample size for a pilot study to estimate the CVintra [Power / Sample Size]
Hello bears,
Yes to the first Q. In a pivotal trial the important uncertainty is that on the T/R ratio. We use this uncertainty it to construct a confidence interval around T/R and to satisfy regulators (hopefully). In a pilot study like the one we discuss here the important uncertainty is that on the estimated CVintra. If we underestimate it, we may underpower the pivotal study (saved only by luck, or a better T/R ratio then expected). I have seen pilots ranging from 12 to perhaps somewhere in the 30'ies, I think. Not exactly sure.
4 to 6 in a pilot trial sounds like it may result in a CVintra that is too poorly estimated. There are no rules, and 'poorly' is in this regard purely my personal subjective unqualified view.
As a good alternative, it is getting more and more common to do a two-stage study in which the first, say, 20 patients are analysed whereafter an interim stats evaluation is carried out; the interim evaluation tries to answers a quesiton like: How many additional patients should be recruited in order to satisfy a goal of 80% (or 90% whatever one likes) power given the CVintra that can be estimated from the first 20?
The latter generally also comes with an expectation that the variability does not increase in the last patients, i.e. the first patients should be representative of the last patients.
Best regards
EM.
❝ Can this CVintra from a pilot study really represent a CVintra from a main study?
❝ What sample size will be required for a pilot study? Usually we use 4-6 subjects as the sample size in a BE pilot study here. I am confused by this question for a while.
Yes to the first Q. In a pivotal trial the important uncertainty is that on the T/R ratio. We use this uncertainty it to construct a confidence interval around T/R and to satisfy regulators (hopefully). In a pilot study like the one we discuss here the important uncertainty is that on the estimated CVintra. If we underestimate it, we may underpower the pivotal study (saved only by luck, or a better T/R ratio then expected). I have seen pilots ranging from 12 to perhaps somewhere in the 30'ies, I think. Not exactly sure.
4 to 6 in a pilot trial sounds like it may result in a CVintra that is too poorly estimated. There are no rules, and 'poorly' is in this regard purely my personal subjective unqualified view.
As a good alternative, it is getting more and more common to do a two-stage study in which the first, say, 20 patients are analysed whereafter an interim stats evaluation is carried out; the interim evaluation tries to answers a quesiton like: How many additional patients should be recruited in order to satisfy a goal of 80% (or 90% whatever one likes) power given the CVintra that can be estimated from the first 20?
The latter generally also comes with an expectation that the variability does not increase in the last patients, i.e. the first patients should be representative of the last patients.
Best regards
EM.
Complete thread:
- Sample Size BA/BE Sriraj 2010-02-26 14:32 [Power / Sample Size]
![[Mix]](https://static.bebac.at/img/mix.png "open in Mix view")
- Sample Size BA/BE Helmut 2010-03-01 14:00
- Sample size for a pilot study to estimate the CVintra yjlee168 2010-03-01 19:25
- Sample size for a pilot study to estimate the CVintra Helmut 2010-03-01 21:01
- Sample size for a pilot study to estimate the CVintra yjlee168 2010-03-01 23:47
- Sample size for a pilot study to estimate the CVintra Helmut 2010-03-03 19:04
- Sample size for a pilot study to estimate the CVintra yjlee168 2010-03-04 22:35
- Sample size for a pilot study to estimate the CVintra Helmut 2010-03-03 19:04
- 80% confidence ? d_labes 2010-03-19 13:02
- 75% confidence... Helmut 2010-03-19 14:12
- Sample size for a pilot study to estimate the CVintra yjlee168 2010-03-01 23:47
- Sample size for a pilot study to estimate the CVintraElMaestro 2010-03-01 22:23
- Sample size for a pilot study to estimate the CVintra yjlee168 2010-03-02 00:02
- Sample size for a pilot study to estimate the CVintra Helmut 2010-03-02 02:19
- Sample size for a pilot study to estimate the CVintra yjlee168 2010-03-29 13:27
- Sample size for a pilot study to estimate the CVintra ElMaestro 2010-03-29 13:39
- Sample size for a pilot study to estimate the CVintra yjlee168 2010-03-29 13:47
- Sequential designs (history and future) Helmut 2010-03-29 14:19
- Sequential designs (history and future) yjlee168 2010-03-29 19:19
- Sequential designs (history and future) Helmut 2010-03-29 20:43
- Sequential designs (history and future) yjlee168 2010-04-01 18:58
- Sequential designs (WinNonlin vs. bear) Helmut 2010-04-02 21:00
- Sequential designs (history and future) yjlee168 2010-04-01 18:58
- Sequential designs (history and future) Helmut 2010-03-29 20:43
- Sequential designs (history and future) yjlee168 2010-03-29 19:19
- Sample size for a pilot study to estimate the CVintra ElMaestro 2010-03-29 13:39
- Sample size for a pilot study to estimate the CVintra yjlee168 2010-03-29 13:27
- Sample size for a pilot study to estimate the CVintra Helmut 2010-03-01 21:01
- Sample size for a pilot study to estimate the CVintra yjlee168 2010-03-01 19:25
- Sample Size BA/BE Helmut 2010-03-01 14:00
Ing. Helmut Schütz