## No ‘R1’ and ‘R2’ in replicate designs [General Sta­tis­tics]

Hi Helmut,

Sorry, because I am lego and I can´t understand all correctly.

❝ There is no ‘R1’ and ‘R2’, only one R repeatedly administered in the sequences in different periods. Say, the sequences are TRR | RTR | RRT. Did the CRO call the first administration in each sequence R1 and the second R2 (while dropping T)?

Yes. But, although this is not the usual approach, if you set the R treatment as R1 and R2, you can make an R1 / R2 comparison, as if they were different treatments, right? And in this way, Is the 90% CI calculated by the CRO well calculated? It seems to me to be a very large interval for a CV of 20%.

❝ As said above, such a ‘comparison’ will not work.

Why? Can you explain?

❝ You tried CI2CV(lower=0.8731, upper=1.4057, design="2x2x2", n=40), right? That’s not what you have. After recoding (wild guess) you have an Incomplete Block Design. Other degrees of freedom,

Yes, I know, but in any case, the difference should be decimals, not changes from 20% to 70%, right? I can't understand how they get a CV of 20% and I get 70%. What's wrong? Besides, with the CI being so wide, it seems to be much more than 20% CV.

❝ These formulas are for a 2×2×2 crossover and are also implemented in CI2CV(). But again, there is only one R. A ‘PE’ and ‘CI’ doesn’t make sense.

❝ You can only calculate the CVwR according to the EMA’s or the FDA’s models. The results will be similar, though quite often the one of the FDA is a bit smaller.

But, although this is not the usual approach, if you set the R treatment as R1 and R2, you can make an R1 / R2 comparison, if you want to do it just for curiosity, considering them as different treatments, it will be feasible, right? And in this way, Is the 90% CI calculated by the CRO well calculated? It seems to me to be a very large interval for a CV of 20%. Or mine?