The AB/BA crossover: past, present and future?

S. Senn*

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

41 Citations (Scopus)


The AB/BA design is reviewed from a historical perspective. Particular attention is paid to the problem of carry-over and various attempts to deal with it. The two-stage procedure, an approach which was popular for many years, is shown to be unsafe. The analysis of AB/BA designs with baseline data is also considered. It is shown that such baselines do not provide a cure for the problem of carry-over; and it is concluded that any rational analysis of such trials will always be dependent on assumptions regarding carry-over, and that it is necessary to pay particular attention to washout periods. Under such circumstances analysis of covariance may be useful. In conclusion, some speculative comments about future lines of research are offered.

Original languageEnglish
Pages (from-to)303-324
Number of pages22
JournalStatistical Methods in Medical Research
Issue number4
Publication statusPublished - Dec 1994
Externally publishedYes


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