```Date: Mon, 12 Mar 2001 13:19:48 +0300 Reply-To: Vasya Dovbnya Sender: "SAS(r) Discussion" From: Vasya Dovbnya Subject: 'Where' statement vs 'Contrast' statement Comments: To: SAS-L@LISTSERV.VT.EDU I have a problem in choosing correct way to perform repeated measures ANOVA. Should I use 'contrast' statement or 'where' statement for comparisons of the Group*Time effect with a control group? Here is my example. I took it from examples for PROC GLM (Example 30.7: Repeated Measures Analysis of Variance) and modified a little bit. It consists of 2 parts. Part 1 uses 'contrast' statement, Part 2 uses 'where' statement. ________ Part 1 proc glm; class Depleted; model Histamine1 Histamine3 Histamine5 = Depleted / nouni; contrast "1-2" Depleted 1 -1 0; contrast "1-3" Depleted 1 0 -1; repeated Time 3(1 3 5) polynomial / summary printe; quit; Output for this procedure shows the following: Source DF Type III SS Mean Square F Value Pr > F G - G H - F Time*1-2 2 0.17222937 0.08611468 0.46 0.6391 0.5330 0.5685 Time*1-3 2 1.60621944 0.80310972 4.25 0.0262 0.0554 0.0451 ________ Part 2 proc glm; where Depleted="N" or Depleted="Y"; class Depleted; model Histamine1 Histamine3 Histamine5 = Depleted / nouni; repeated Time 3(1 3 5) polynomial / summary printe; quit; proc glm; where Depleted="N" or Depleted="han"; class Depleted; model Histamine1 Histamine3 Histamine5 = Depleted / nouni; repeated Time 3(1 3 5) polynomial / summary printe; quit; Output for these procedures shows the following: Source DF Type III SS Mean Square F Value Pr > F G - G H - F Time*Depleted 2 0.17222937 0.08611468 1.95 0.1929 0.2215 0.2148 Time*Depleted 2 1.60621944 0.80310972 3.55 0.0481 0.0827 0.0745 ________ I have no idea, why Type III SS is the same for both parts but the F-values differ. Please, help! Thanks! Vasya. ```

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