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The three variants of open cohort sampling schemes that we will consider, illustrated for a four‐period design. Groups of participants measured in multiple periods are denoted with repeated letters and colours. Rotation sampling scheme 1 has an in‐for‐2 sampling structure, and rotation sampling scheme 2 has an in‐for‐3 sampling structure [Colour figure can be viewed at http://wileyonlinelibrary.com]
