RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 1 THE DATA AS SAS SEES IT 22:18 Wednesday, November 16, 2005 Obs Group Drug yy 1 HD Drug 51 2 HD Drug 57 3 HD Drug 48 4 HD Drug 55 5 HD NoDrug 70 6 HD NoDrug 72 7 HD NoDrug 68 8 HD NoDrug 75 9 NonHD Drug 67 10 NonHD Drug 60 11 NonHD Drug 58 12 NonHD Drug 65 13 NonHD NoDrug 50 14 NonHD NoDrug 45 15 NonHD NoDrug 55 16 NonHD NoDrug 52 RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 2 PROC MEANS OUTPUT 22:18 Wednesday, November 16, 2005 Obs Group Drug _TYPE_ _FREQ_ yy 1 HD Drug 3 4 52.75 2 HD NoDrug 3 4 71.25 3 NonHD Drug 3 4 62.50 4 NonHD NoDrug 3 4 50.50 RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 3 INTERACTION PLOT of Drug vs. Group 22:18 Wednesday, November 16, 2005 NOTE THAT THE INTERACTION IS STRONGLY VISIBLE IN THE CHANGE OF SIGN OF H-N (HD minus NonHD) Plot of yy*Drug. Symbol is value of Group. yy | 80 + | | | | H 70 + | | | | N 60 + | | | | H 50 + N ---+----------------------------------------------+-- Drug NoDrug Ritalin or NoRitalin RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 4 FULL FACTORIAL MODEL for two factors 22:18 Wednesday, November 16, 2005 The GLM Procedure Class Level Information Class Levels Values Group 2 HD NonHD Drug 2 Drug NoDrug Number of Observations Read 16 Number of Observations Used 16 RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 5 FULL FACTORIAL MODEL for two factors 22:18 Wednesday, November 16, 2005 The GLM Procedure Dependent Variable: yy Sum of Source DF Squares Mean Square F Value Pr > F Model 3 1093.500000 364.500000 24.10 <.0001 Error 12 181.500000 15.125000 Corrected Total 15 1275.000000 R-Square Coeff Var Root MSE yy Mean 0.857647 6.563860 3.889087 59.25000 Source DF Type I SS Mean Square F Value Pr > F Group 1 121.0000000 121.0000000 8.00 0.0152 Drug 1 42.2500000 42.2500000 2.79 0.1205 Group*Drug 1 930.2500000 930.2500000 61.50 <.0001 Source DF Type III SS Mean Square F Value Pr > F Group 1 121.0000000 121.0000000 8.00 0.0152 Drug 1 42.2500000 42.2500000 2.79 0.1205 Group*Drug 1 930.2500000 930.2500000 61.50 <.0001 RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 6 MAIN EFFECTS only 22:18 Wednesday, November 16, 2005 (THIS IS A BAD IDEA HERE since it includes the INTERACTIONS with the error) NOTE THAT nothing is significance now due to the inflated SSE term. The GLM Procedure Class Level Information Class Levels Values Group 2 HD NonHD Drug 2 Drug NoDrug Number of Observations Read 16 Number of Observations Used 16 RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 7 MAIN EFFECTS only 22:18 Wednesday, November 16, 2005 (THIS IS A BAD IDEA HERE since it includes the INTERACTIONS with the error) NOTE THAT nothing is significance now due to the inflated SSE term. The GLM Procedure Dependent Variable: yy Sum of Source DF Squares Mean Square F Value Pr > F Model 2 163.250000 81.625000 0.95 0.4104 Error 13 1111.750000 85.519231 Corrected Total 15 1275.000000 R-Square Coeff Var Root MSE yy Mean 0.128039 15.60787 9.247661 59.25000 Source DF Type I SS Mean Square F Value Pr > F Group 1 121.0000000 121.0000000 1.41 0.2555 Drug 1 42.2500000 42.2500000 0.49 0.4945 Source DF Type III SS Mean Square F Value Pr > F Group 1 121.0000000 121.0000000 1.41 0.2555 Drug 1 42.2500000 42.2500000 0.49 0.4945 RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 8 ONE-WAY ANOVA on cells for two factors 22:18 Wednesday, November 16, 2005 Which COMBINATIONS of factor levels are different? The GLM Procedure Class Level Information Class Levels Values cell 4 HD Drug HD NoDrug NonHD Drug NonHD NoDrug Number of Observations Read 16 Number of Observations Used 16 RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 9 ONE-WAY ANOVA on cells for two factors 22:18 Wednesday, November 16, 2005 Which COMBINATIONS of factor levels are different? The GLM Procedure Dependent Variable: yy Sum of Source DF Squares Mean Square F Value Pr > F Model 3 1093.500000 364.500000 24.10 <.0001 Error 12 181.500000 15.125000 Corrected Total 15 1275.000000 R-Square Coeff Var Root MSE yy Mean 0.857647 6.563860 3.889087 59.25000 Source DF Type I SS Mean Square F Value Pr > F cell 3 1093.500000 364.500000 24.10 <.0001 Source DF Type III SS Mean Square F Value Pr > F cell 3 1093.500000 364.500000 24.10 <.0001 RITALIN DATA: LOOKING FOR AN INTERACTION - YOURNAME 10 ONE-WAY ANOVA on cells for two factors 22:18 Wednesday, November 16, 2005 Which COMBINATIONS of factor levels are different? The GLM Procedure Duncan's Multiple Range Test for yy NOTE: This test controls the Type I comparisonwise error rate, not the experimentwise error rate. Alpha 0.05 Error Degrees of Freedom 12 Error Mean Square 15.125 Number of Means 2 3 4 Critical Range 5.992 6.272 6.441 Means with the same letter are not significantly different. D u n c a n G r o u p i n g Mean N cell A 71.250 4 HD NoDrug B 62.500 4 NonHD Drug C 52.750 4 HD Drug C C 50.500 4 NonHD NoDrug