CROSSOVER DESIGN Repeated Measures meets Latin Squares 1

LAYOUT FOR CROSSOVER DESIGN  Group III Subject1…910…18 Time 1A…AB B 2B…BA A 2

FIRST NINE SUBJECTS AT TIME 1  SubjectGroupTimeDrugY 111A A A A A A A A A39.1 3

CROSSOVER MODEL (SPLIT–PLOT UNIVARIATE ANALYSIS)  Y ijkl =µ+G i +S (i)j Between Subjects  +T k +D l +ε ijkl Within Subjects 4

ENTER ALL TERMS IN THE MODEL AS FIXED TO GET ALL SS FROM JMP  5

THIS GIVES ALL MODEL AND ERROR SS  6

IF WE SPECIFY SUBJECT AS RANDOM  7

SUBJECT(GROUP) TESTS GROUP, RESIDUAL TESTS THE WITHIN TERMS  8

USUALLY HOPE TIME IS NOT SIGNIFICANT, BUT AT LEAST WE CONTROLLED FOR IT  9

WHAT WOULD HAPPEN IF WE BELIEVED OUR MODEL AND TESTED DRUG A AT TIME 1 AND DRUG B AT TIME 2? Hint is next slide….. 10

CONSIDER THE DRUG EFFECT  11

PLOT TIME*DRUG  12

MORAL: CROSSING IS GOOD  Main Effects would have been confounded 13

ACTUALLY ONLY FOUR DISTINCT PREDICTED VALUES. WHY?  14

NOW CHECK NORMALITY 15