lizhao
☆    

US,
2016-02-17 20:01
(2961 d 13:41 ago)

Posting: # 16003
Views: 8,554
 

 how to construct confidence interval for un-transformed metric? [Power / Sample Size]

Dear all,

For clinical endpoints, I suppose the log-normal distribution doesn't hold, therefore I should use un-transformed data to construct the 90% confidence interval? Then it would be the confidence interval of mean Test/Reference ratio? Am I correct?

But then, would the acceptance limits become 80% to 120% instead? If somebody could help me out, it would be greatly appreaciated!!

Thanks!
jag009
★★★

NJ,
2016-02-17 21:43
(2961 d 11:59 ago)

@ lizhao
Posting: # 16004
Views: 7,335
 

 how to construct confidence interval for un-transformed metric?

mittyri
★★  

Russia,
2016-02-17 23:34
(2961 d 10:07 ago)

@ lizhao
Posting: # 16005
Views: 7,369
 

 how to construct confidence interval for un-transformed metric?

Hi lizhao,

Some example from the ordinary guidance:
[image]

❝ For clinical endpoints, I suppose the log-normal distribution doesn't hold, therefore I should use un-transformed data to construct the 90% confidence interval? Then it would be the confidence interval of mean Test/Reference ratio? Am I correct?


It could be the difference or the ratio.
It is common practice to suppose normal distribution of clinical endpoints.
BTW be aware, are you sure that your clinical endpoint is distributed normally?

❝ But then, would the acceptance limits become 80% to 120% instead?


Exactly (+/-0.2)

Kind regards,
Mittyri
Helmut
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Homepage
Vienna, Austria,
2016-02-18 14:38
(2960 d 19:03 ago)

@ mittyri
Posting: # 16006
Views: 7,262
 

 Fieller’s confidence interval

Dear all,

don’t mix up differences with percentages. It’s up to you (maybe supported by a scientific advice) to consider which deviation of the endpoint is clinically relevant.
See these threads: #11431, #9534, #1870 and the references given within them.

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lizhao
☆    

US,
2016-02-22 21:20
(2956 d 12:22 ago)

@ Helmut
Posting: # 16017
Views: 7,035
 

 Fieller’s confidence interval

Dear Helmut and all,

Thank you very much for your help! I have done some literature search on Fieller's confidence interval and I am ready to use R to construct the confidence interval. I wonder if you know where I can find some R code/package to compute Fieller's confidence interval? Also, I think the computation depends on parallel or crossover design, as the intrasubject variability would be different? Am I correct?

Thanks a lot!
yjlee168
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Homepage
Kaohsiung, Taiwan,
2016-02-23 09:23
(2956 d 00:18 ago)

@ lizhao
Posting: # 16018
Views: 7,060
 

 Fieller’s confidence interval

Hi lizhao,

There is another easy way to calculate Fieller's CI. See this link. Also if you prefer using R/package, see the package mratios. You should be able to find the R codes for Fieller's CI from package mratios. Never use both before. Try it yourself.

All the best,
-- Yung-jin Lee
bear v2.9.1:- created by Hsin-ya Lee & Yung-jin Lee
Kaohsiung, Taiwan https://www.pkpd168.com/bear
Download link (updated) -> here
d_labes
★★★

Berlin, Germany,
2016-02-23 10:08
(2955 d 23:33 ago)

@ lizhao
Posting: # 16021
Views: 7,002
 

 Rescue approaching – PowerTOST

Dear lizhao,

package PowerTOST aka "Swiss army knife for lazy guys dealing with BE studies" has a function CI.RatioF() for calculating the Fieller's confidence interval for the designs "2x2" and "parallel" given estimates of the GMR, CV and CVb(between).

The theoretical background can be found in:

Hauschke et al.
"Sample Size Determination for Proving Equivalence Based on the Ratio of Two Means For Normally Distributed Data"
Statist. Med. 18, 93-105 (1999)

or

Hauschke D., Steinijans V. and Pigeot I.
"Bioequivalence Studies in Drug Development"
Chapter 10., John Wiley & Sons, Chichester (2007)


Regards,

Detlew
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