University of Groningen
Evaluation and analysis of stepped wedge designs
Zhan, Zhuozhao
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Publication date:
2018
Link to publication in University of Groningen/UMCG research database
Citation for published version (APA):
Zhan, Z. (2018). Evaluation and analysis of stepped wedge designs: Application to colorectal cancer
follow-up. Rijksuniversiteit Groningen.
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Propositions
accompanying the dissertation
E
VALUATION AND ANALYSIS OF STEPPED WEDGE DESIGNSAPPLICATION TO COLORECTAL CANCER FOLLOW-UP
1. A stepped wedge design is a strong candidate for pragmatic trials. (This the-sis)
2. The main advantage of the stepped wedge design for the CEAwatch trial was the inclusion of a large number of patients mainly due to the motivating fea-ture of the design that in the end all participants would be switched to the new follow-up protocol. (This thesis)
3. Not all treatment-period interaction effects are estimable without making assumptions in stepped wedge trials (This thesis)
4. To ensure an unbiased estimate of the time-dependent treatment effect in a stepped wedge trial, it is necessary to take into account the association between the switch moment and the outcomes before the switching. (This thesis)
5. Data from at least three periods are needed in a stepped wedge trial to ad-dress a suspected accumulation of treatment effect. A pre-post measure-ment scheme is not recommended. (This thesis)
6. Dynamic recruitment can help protect the study against healthy-survivor bias and unbalances in confounders due to attrition, but it can cannot com-pletely eliminate the risk of bias. (This thesis)
7. When planning a stepped wedge trial, it is important to make sure that the time between two switching moments have the correct length to be able to extract sufficient information from both control and intervention periods. This is particularly important for survival-type of outcomes. (This thesis) 8. Essentially, all models are wrong, but some are useful. (G. E. P. Box)
9. To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. (R. A. Fisher)
10. Most real-life statistical problems have one or more nonstandard features. There are no routine statistical questions, only questionable statistical rou-tines. (J. M. Hammersley)
