Bioequivalence and Bioavailability Forum

90% confidence interval for R_dnm [Study As­sess­ment]

posted by d_labes  – Berlin, Germany, 2019-01-05 15:01 (2268 d 08:20 ago) – Posting: # 19731
Views: 20,618

Dear Shuanghe,

First: Happy New Year to You and to All.

❝ Man, I should checked here before I started my work. It could save me a lot of time...

Late but hopefully not too late insight. As I sometimes stated: All answers (of asked or not asked questions) are here. You only have to dig out what you are interested in.

❝ Recently I was helping one of my colleagues for dose proportionality study and power model in Smith's article is the preferred method. While I did figured out the "correct" degree of freedom method and reproduce all reported results such as intercept, slope, and 90% CI of those values, ρ₁, ρ₂, the ratio of dose-normalised geometric mean value R_dnm,..., I could not figure out how Smith obtained the 90% confidence interval for R_dnm (0.477, 0.698).

Can you please elaborate where your difficulties arose? Able to obtain a point estimate of R_dnm but no 90% CI thereof?

❝ ...

❝ In his article (pp.1282, 2nd paragraph), Smith wrote that "[i]The 90% CI for the difference in log-transformed means was calculated within the MIXED procedure. Exponentiation of each limit and division by r gave the 90% CI for R_dnm ...

For me this is a dubious description (the whole paragraph) I don't understand at all. Difference in log-transformed means of what?

I would go with the formula of R_dnm

R_dnm = r^(beta1 - 1)
with r= ratio of highest to lowest dose and beta1=slope

Use this with the point estimate of beta1 from your model and its 90% CI limits and you obtain the 90% CI of R_dnm if I'm correct.
Example Cmax in Table 2 of the Smith et al. paper:
beta1 = 0.7615 (0.679, 0.844)
R console:
c(10^(0.7615-1), 10^(0.679-1), 10^(0.844-1))
[1] 0.5774309 0.4775293 0.6982324
Smith reported in Table 2:
    0.577    (0.477,    0.698)
Good enough?

Hope this helps.

Complete thread:

• Dose Proportionality and Variance AngusMcLean 2016-05-11 16:55 [Study As­sess­ment] 
  • More information, please Helmut 2016-05-12 14:34
    • More information, please AngusMcLean 2016-05-13 16:40
      • Setup in Phoenix/WinNonlin Helmut 2016-05-14 02:26
        • Setup in Phoenix/WinNonlin AngusMcLean 2016-05-14 18:54
          • Setup in Phoenix/WinNonlin Helmut 2016-05-15 14:47
            • Setup in Phoenix/WinNonlin AngusMcLean 2016-05-15 15:17
              • Phoenix 64 Warning Helmut 2016-05-15 15:56
                • Phoenix 64 Warning AngusMcLean 2016-05-15 20:11
                  • OT: imperial vs. metric units Helmut 2016-05-16 16:26
              • Setup in Phoenix/WinNonlin ElMaestro 2016-05-15 20:54
                • Setup in Phoenix/WinNonlin AngusMcLean 2016-05-15 22:30
        • Setup in Phoenix/WinNonlin AngusMcLean 2016-05-16 21:00
          • NCSS vs. PHX/WNL vs. SAS Helmut 2016-05-17 01:50
            • NCSS vs. PHX/WNL vs. SAS - Validation? mittyri 2016-05-18 08:23
              • Diagnostics ElMaestro 2016-05-18 09:20
                • Diagnostics: R and Phoenix Helmut 2016-05-18 15:14
                  • Diagnostics: R zizou 2016-05-22 19:07
                    • Diagnostics: R Helmut 2016-05-23 01:22
                      • SASian potpourri d_labes 2016-05-24 12:02
                        • Compilation Helmut 2016-05-24 14:27
                          • REML or not d_labes 2016-05-24 16:33
                            • complete or not Helmut 2016-05-24 16:57
                          • Compilation AngusMcLean 2016-05-26 16:46
                            • doubts about NCSS Helmut 2016-05-26 19:13
                              • Doubts about NCSS zizou 2016-05-26 23:38
                          • Compilation AngusMcLean 2016-05-28 00:51
                            • Kenward-Roger? Helmut 2016-05-28 15:59
                          • 90% confidence interval for R_dnm Shuanghe 2019-01-04 17:45
                            • 90% confidence interval for R_dnmd_labes 2019-01-05 14:01
                              • Visualizing lmer and limits mittyri 2019-01-06 17:00
                                • Visualizing lmer and limits Shuanghe 2019-01-07 11:05
                                • Visualizing lmer and limits d_labes 2019-01-07 15:08
                                  • Visualizing lmer and limits mittyri 2019-01-13 23:53
                              • 90% confidence interval for R_dnm Shuanghe 2019-01-07 10:53
                                • 90% confidence interval for R_dnm d_labes 2019-01-07 15:17
                                  • 90% confidence interval for R_dnm Shuanghe 2019-01-07 17:11
                                    • 90% confidence interval for R_dnm d_labes 2019-01-07 18:24
                                    • offtop: greek letters and tables mittyri 2019-01-08 00:19
                                      • OT: greek letters and symbols Helmut 2019-02-02 16:04
              • Smith’s paper Helmut 2016-05-18 14:44
                • Smith’s paper d_labes 2019-01-05 15:00