TY - JOUR
T1 - Randomized clinical trials with a pre- and a post-treatment measurement: repeated measures versus ANCOVA models
AU - Winkens, B.
AU - van Breukelen, G.J.P.
AU - Schouten, H.J.A.
AU - Berger, M.P.F.
PY - 2007/1/1
Y1 - 2007/1/1
N2 - Repeated measures (RM) and ANCOVA models are compared with respect to treatment effect estimation in randomized clinical trials with a pre- and a post-treatment measure. The covariance matrices of repeated measures are assumed to be I) homogeneous or II) heterogeneous across groups. In situation I, ANCOVA is preferred to RM, because the estimated variance of the treatment effect estimator is unbiased for ANCOVA and biased downwards for RM. In situation II, RM with Kenward and Roger's adjustment is preferred to ANCOVA, because the ANCOVA variance estimator does not correct for unknown pre-treatment expectation. The results are illustrated with an example.
AB - Repeated measures (RM) and ANCOVA models are compared with respect to treatment effect estimation in randomized clinical trials with a pre- and a post-treatment measure. The covariance matrices of repeated measures are assumed to be I) homogeneous or II) heterogeneous across groups. In situation I, ANCOVA is preferred to RM, because the estimated variance of the treatment effect estimator is unbiased for ANCOVA and biased downwards for RM. In situation II, RM with Kenward and Roger's adjustment is preferred to ANCOVA, because the ANCOVA variance estimator does not correct for unknown pre-treatment expectation. The results are illustrated with an example.
U2 - 10.1016/j.cct.2007.04.002
DO - 10.1016/j.cct.2007.04.002
M3 - Article
C2 - 17524958
SN - 1551-7144
VL - 28
SP - 713
EP - 719
JO - Contemporary Clinical Trials
JF - Contemporary Clinical Trials
IS - 6
ER -