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On the Analysis of Crossover Designs Dallas E. Johnson Professor Emeritus Kansas State University

On the Analysis of Crossover Designs Dallas E. Johnson Professor Emeritus Kansas State University. dejohnsn@ksu.edu 785-532-0510 (Office) 785-539-0137 (Home) Dallas E. Johnson 1812 Denholm Dr. Manhattan, KS 66503-2210. Note that . and.

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On the Analysis of Crossover Designs Dallas E. Johnson Professor Emeritus Kansas State University

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  1. On the Analysis of Crossover Designs Dallas E. Johnson Professor Emeritus Kansas State University

  2. dejohnsn@ksu.edu 785-532-0510 (Office) 785-539-0137 (Home) Dallas E. Johnson 1812 Denholm Dr. Manhattan, KS 66503-2210

  3. Note that and

  4. To answer these kinds of questions, Shanga simulated two period/two treatment crossover experiments satisfying four different conditions: (1) no carryover and equal variances (C0V0), (2) no carryover and unequal variances(C0V1), (3) carryover and equal variances (C1V0), and (4) carryover and unequal variances (C1V1).

  5. Each of 1000 sets of data under each of these conditions was analyzed four different ways assuming: (1) no carryover and equal variances (C0V0), (2) no carryover and unequal variances(C0V1), (3) carryover and equal variances (C1V0), and (4) carryover and unequal variances (C1V1).

  6. PROCMIXED; TITLE2'EQUAL VARIANCES'; CLASSES SEQ PERIOD TRT PERSON; MODEL PEF=SEQ TRT PERIOD/DDFM=SATTERTH; REPEATED TRT/SUBJECT=PERSON(SEQ) TYPE=CS; LSMEANS TRT /PDIFF; RUN; PROCMIXED; TITLE2'UNEQUAL VARIANCES'; CLASSES SEQ PERIOD TRT PERSON; MODEL PEF=SEQ TRT PERIOD/DDFM=SATTERTH; REPEATED TRT/SUBJECT=PERSON(SEQ) TYPE=CSH; LSMEANS TRT /PDIFF; RUN;

  7. Tests for equal treatment effects.

  8. Tests for equal treatment effects.

  9. NOTE: Failing to assume carryover when carryover exists invalidates the tests for equal treatment effects and the invalidation generally gets worse as the

  10. TITLE1'A THREE PERIOD/THREE TRT DESIGN'; TITLE2'ANALYSIS ASSUMES NO CARRY-OVER'; PROCMIXED; TITLE3'ANALYSIS USING SAS-MIXED'; CLASSES SEQ PER TRT SUBJ; MODEL Y=SEQ TRT PER/DDFM=SATTERTH; RANDOM SUBJ(SEQ); LSMEANS TRT PER/PDIFF; RUN;

  11. Analyses assuming carryover.

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