Bioequivalence and Bioavailability Forum

The mysterious ρ -between or within studies [General Statistics]

posted by Helmut – Vienna, Austria, 2018-02-11 18:31 (2596 d 03:44 ago) – Posting: # 18396
Views: 17,261

Dear Detlew

❝ That's not the whole truth about the state of affairs :no: .

❝ The question is: Correlation of treatment differences between studies or within studies.

❝

❝ For the latter I recall you two references:

❝ Phillips KF.

❝ Power for Testing Multiple Instances of the Two One-Sided Tests Procedure

❝ Int J Biostat. 2009;5(1):Article 15. doi:10.2202/1557-4679.1169

❝

❝ Quote from Kem Phillips:

❝ "The correlation will usually be difficult to estimate, unless a similar experiment has been conducted...".

❝ That smells for me like within a study.

Yep, then I expect a high correlation (based on my limited knowledge of PK). For my data sets I get with

pearson <- cor.test(log(study$AUC), log(study$Cmax))

rho[set, "estimate"] <- pearson$estimate

rho[set, "lower"]    <- as.numeric(pearson$conf.int)[[1]]

rho[set, "upper"]    <- as.numeric(pearson$conf.int)[[2]]

summary(rho, digits=5)



    estimate           lower               upper      

 Min.   :0.20123   Min.   :-0.094923   Min.   :0.40858

 1st Qu.:0.70335   1st Qu.: 0.516584   1st Qu.:0.82721

 Median :0.81713   Median : 0.677607   Median :0.89959

 Mean   :0.77413   Mean   : 0.633948   Mean   :0.86544

 3rd Qu.:0.90122   3rd Qu.: 0.827646   3rd Qu.:0.94461

 Max.   :0.98928   Max.   : 0.977336   Max.   :0.99494

IIRC, Chow & Liu state somewhere that the mean of within-subject ratios is a biased estimate…

Another question: What is a “similar experiment”? Given the dispersion in the summary above I would rather say that trying to get an estimate across different drugs (or even for the same drug but IR/IR and MR/MR) is futile. Will try again with the analyte as a factor.

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

The quality of responses received is directly proportional to the quality of the question asked. 🚮
Science Quotes

Complete thread:

Power and type I adjustment for 222BE when several PK prams considered Louis52 2018-02-07 21:04 [General Statistics]
- Power and type I adjustment for 222BE when several PK prams considered ElMaestro 2018-02-07 22:37
- Power of two combined TOST d_labes 2018-02-08 14:12
  - The mysterious ρ Helmut 2018-02-08 21:40
    - ρ ρ ρ your boat ElMaestro 2018-02-09 09:58
      - ρ ρ ρ your boat Helmut 2018-02-09 19:20
    - ...and a bonus question ElMaestro 2018-02-09 11:32
      - ...and a bonus question Helmut 2018-02-09 19:43
        
        If u see a BEar don't forget to R oaρ Astea 2018-02-09 20:47
        
        package install failed d_labes 2018-02-11 13:23
    - The mysterious ρ -between or within studies d_labes 2018-02-11 15:57
      - The mysterious ρ -between or within studiesHelmut 2018-02-11 17:31
        
        The mysterious ρ -between or within studies d_labes 2018-02-11 19:21
        
        The mysterious ρ within studies Helmut 2018-02-11 22:44
        
        The mysterious ρ within studies nobody 2018-02-12 09:08
      - The mysterious ρ -between or within studies Astea 2018-02-11 17:34
        
        The mysterious ρ -between or within studies d_labes 2018-02-11 19:36
        The mysterious ρ within studies Helmut 2018-02-11 22:48
- Power and type I adjustment for 222BE when several PK prams considered ElMaestro 2018-02-11 18:43
  - Power and type I adjustment for 222BE when several PK prams considered nobody 2018-02-12 09:10
    - reminds me of something ElMaestro 2018-02-12 09:18
      - reminds me of something nobody 2018-02-12 09:38
        
        Hammer to fall Astea 2018-02-12 18:37
        
        Put the sickle to the corn Helmut 2018-02-13 01:37
        
        Put the sickle to the corn Astea 2018-02-13 08:27
        
        Put the sickle to the corn Helmut 2018-02-13 12:45
        
        Put the sickle to the corn Relaxation 2018-02-13 10:37
        
        multiple units, lag-times Helmut 2018-02-13 13:31

The mysterious ρ -between or within studies [General Sta­tis­tics]

Complete thread:

The mysterious ρ -between or within studies [General Statistics]