Oops. Oops. [Regulatives / Guidelines]

posted by d_labes  – Berlin, Germany, 2011-11-25 14:54 (4955 d 14:06 ago) – Posting: # 7723
Views: 8,874

Dear Helmut!

Quite a time ago I had promised to come out with a simulation including subject variability and intra-subject correlation.

Due to spare time I could not until now consider this.
Before posting my results I would like to compare it to your code.

Inspecting it I have some doubts:

# massacrating out everything related to R2

# means that when T was before R1 we now have a seq 1 otherwise a seq 2

seq2 <- as.factor(rep(c(1,1, 2,2, 1,1, 1,1, 2,2, 2,2), size/6))

sub2 <- as.factor(rep(1:size, each = 2))

per2 <- as.factor(rep(1:2, size))

trt2 <- as.factor(rep(c(1,2, 2,1, 1,2, 1,2, 2,1, 2,1), size/6))


Must the EMA guidance interpreted in this way, i.e. analysing the dataset with 'pseudo' periods and sequences? Or should it interpreted the way which is employed in the Q&A for the replicate design (intra-subject variability of the reference). That means only massacre out the data concerning R2 but retaining the original periods and sequences. :ponder:

FullModel <- lm(log(y1) ~ 0 + seq1 + sub1 %in% seq1 + per1 + trt1)

FMDelta   <- mean(log(y1)[trt1==1])-mean(log(y1)[trt1==2])

FMdf      <- aov(FullModel)$df.residual

FMMSE     <- summary(FullModel)$sigma^2/FMdf

FMlo      <- 100*exp(FMDelta - qt(1-0.05,FMdf)*sqrt(2*FMMSE/size))

FMhi      <- 100*exp(FMDelta + qt(1-0.05,FMdf)*sqrt(2*FMMSE/size))

FMCI      <- FMhi - FMlo

FMCVintra <- c(FMCVintra, sqrt(exp(FMMSE)-1))


At least the code for FMMSE has stolen my sleep :confused:. According to the help page of lm.summary() "... sigma - the square root of the estimated variance of the random error" and IMHO then the MSE is sigma^2 without the division by the degrees of freedom!
Check this out via anova(FullModel)["Residuals","Mean Sq"]==summary(FullModel)$sigma^2 .
Or did I miss sumfink here?

Regards,

Detlew

Complete thread:

UA Flag
Activity
 Admin contact
23,424 posts in 4,927 threads, 1,676 registered users;
44 visitors (0 registered, 44 guests [including 8 identified bots]).
Forum time: 06:00 CEST (Europe/Vienna)

Complex, statistically improbable things are by their nature
more difficult to explain than
simple, statistically probable things.    Richard Dawkins

The Bioequivalence and Bioavailability Forum is hosted by
BEBAC Ing. Helmut Schütz
HTML5