Furthermore, the SEs obtained from bootstrapping the ascertained data are comparable to the full-data bootstrap, suggesting that there is no need to bootstrap the optimal matching step.
However, this sampling scheme may not be optimal, and in fact it has been shown (Glidden and Liang 2002; Noh et al. 2005) that the analysis of the ascertained data is sensitive to mis-specification of the random-effect distribution.
Previous studies (Glidden and Liang 2002; Noh et al. 2005) indicated that the exact likelihood analysis of ascertained data is sensitive to mis-specification of the random-effect distribution.
Exposure is satisfactorily ascertained if data were acquired from secure records.
Before subjecting age, years of education, intelligence/attention scores and VLMT performance during sham stimulation across both groups to parametrical statistical testing, we ascertained that data were normally distributed (Kolmogorov-Smirnov-test). T-tests for independent samples did not reveal significant differences in these control variables among groups.
To repeat the work and ascertain that data were not affected by a systemic difference that occurred over the 12-month period, 5,000 BAC clones each from the 3AS and 3DS libraries were re-fingerprinted side-by-side, i.e., equal numbers of 3AS and 3DS clones were included in each fingerprinting and fragment-sizing run.
A total of 251 newborns with Down syndrome and 396 electively aborted fetuses with Down syndrome were ascertained (data from Czech Congenital Anomalies Register); 61% of pregnancies with Down syndrome are electively aborted [ 22].
Angiotensin-II, ANP, and BNP mRNA were variable in all exposure groups including controls, and no consistent differences could be ascertained (data not shown).
Exposure is satisfactorily ascertained if data are collected from a secure record.
Each ELISA plate contained positive and negative checks, and the validity of each assay was ascertained before data was processed.
