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Back to the forum  Query: 2018-05-21 13:04 CEST (UTC+2h)
 

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

posted by d_labes - Berlin, Germany, 2018-02-11 19:21  - Posting: # 18399
Views: 2,264

Dear Helmut,

» 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

Thanks for that numbers.

» Another question: What is a “similar experiment”?

Good question. Another question. Duno. Pilot study?
For me the hole rho story is a mystery. And rather academic.
Nobody is acting according to that theory. Not at least because the understanding of what value rho shoud have or how it could be estimated.

Taking the greater sample size from the two estimations worked in the past. So what?
Theoretically this would be the case if rho ~ 1 since then the combined power of the two TOST is the minimum of the individual powers. That would be my favoured candidate :-D.
Be warned: rho=1 throws an error in sampleN.2TOST().

Regards,

Detlew

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