Brug af baseline og andre prædiktorer i randomiserede, kontrollerede forsøg :: Draft
{% newthought “Randomiserede, kontrollerede kliniske forsøg” %} (engelsk: randomized controlled trials eller RCT) er den gyldne standard indenfor kliniske forsøg, da dette forsøgsdesign giver direkte mulighed for at estimere kausale effekter af en behandling. Ofte registreres hver forsøgsenhed to gange: en gang ved baseline inden behandlingen startes og en gang efter, men i videnskabelige artikler er der stor forskel på, hvordan baseline-værdierne — og andre baggrundsvariable — bliver brugt.
http://www.jerrydallal.com/lhsp/prepost.htm https://stats.stackexchange.com/questions/15713/is-it-valid-to-include-a-baseline-measure-as-control-variable-when-testing-the-e https://stats.stackexchange.com/questions/15104/should-the-difference-between-control-and-treatment-be-modelled-explicitly-or-imp/15108#15108 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC34605/ file:///Users/cld189/Downloads/Allison.SM90%20Change%20scores%20as%20dependent%20variables%20in%20regression%20analysis.pdf https://stats.stackexchange.com/questions/83277/using-control-variables-in-experiments
Der er typisk to steder, hvor baseline-værdierne fra et RCT bliver brugt.
https://www.nytimes.com/2017/11/28/magazine/a-failure-to-heal.html?smid=pl-share
Brug af baseline-værdier til at validere randomiseringen
Store tabel 1
Brug af baseline-værdier i analysen af af behandlingseffekten
Brug af baseline-værdier
Lad os lige starte med at slå fast, at der ikke er nogle generelle, formelle krav til udformningen eller indholdet af den “store” tabel 1. Med andre ord skal indholdet af tabellen svare til den historie … og hvis Hvis formålet er at præsentere de indsamlede data, så
http://www.sciencedirect.com/science/article/pii/S2221169115303671
Inklusion af andre prædiktorer
https://stats.stackexchange.com/questions/83277/using-control-variables-in-experiments
2 down vote accepted From a frequentist perspective, an unadjusted comparison based on the permutation distribution can always be justified following a (properly) randomized study. A similar justification can be made for inference based on common parametric distributions (e.g., the tt distribution or FF distribution) due to their similarity to the permutation distribution. In fact, adjusting for covariates—when they are selected based on post-hoc analyses—actually risks inflating the Type I error. Note that this justification has nothing to do with the degree of balance in the observed sample, or with the size of the sample (except that for small samples the permutation distribution will be more discrete, and less well approximated by the tt or FF distributions).
That said, many people are aware that adjusting for covariates can increase precision in the linear model. Specifically, adjusting for covariates increases the precision of the estimated treatment effect when they are predictive of the outcome and not correlated with the treatment variable (as is true in the case of a randomized study). What is less well known, however, is that this does not automatically carry over to non-linear models. For example, Robinson and Jewell [1] show that in the case of logistic regression, controlling for covariates reduces the precision of the estimated treatment effect, even when they are predictive of the outcome. However, because the estimated treatment effect is also larger in the adjusted model, controlling for covariates predictive of the outcome does increase efficiency when testing the null hypothesis of no treatment effect following a randomized study.
[1] L. D. Robinson and N. P. Jewell. Some surprising results about covariate adjustment in logistic regression models. International Statistical Review, 58(2):227–40, 1991.