l'v\ \ ANNOTATED COMPUTER OUPUT FOR SPLIT PLOT DESIGN: GENSTAT ANOVA by W.T. Federer, Z.D. Feng, and N.J. Miles-McDermott Mathematical Sciences Institute, Cornell University, Ithaca, NY ABSTRACT In order to provide an understanding of covariance split plot without designs, the covariate. performed. the .e analyses conducted on an analysis with the a data set covariate is The third example has a different experiment design for whole plots and within Then are first analyses for a whole the covariate is constant for all split plots plot. Computer packages may only give portions of the analysis correctly. to obtain a portion Some packages require two procedural calls of the correct results. GENSTAT requires only one procedural call. INTRODUCTION This is part of a continuing project that produces annotated computer output for the analysis of balanced split plot experiments with covariates. The complete project will involve processing three examples on SAS/GLM, SYSTAT/MGLH. BMDP/2V, SPSS-X/MANOVA, GENSTAT/ANOVA, and Only univariate results are considered. We show here the results from GENSTAT ANOVA. For Example 1, the data are artificial and were constructed for ease of computation; the experiment design for the whole plots is a randomized plot treatments are complete block and the split randomly allocated to the split plot experimental units within each whole plot. Example 2 is the same as Example 1 except that a covariate varies from split plot to split plot. The data for Example 3 come from an experiment wherein the whole plot treatments were laid out in a treatments were units completely randomized design and the split plot randomly within each from whole allotted to whole plot. plot to whole the split plot experimental The value of the covariate varies plot but is constant for all split plots within a whole plot treatment. We present the elementary steps. computational Simple hypothetical data are used for the first two examples so that it is easy to number provide all is obtained. computations. The detailed Some third computations to illustrate how each readers may wish to skip example comes from Winer the detailed (1971). The detailed computations are given in his book (p. 803). Data SP-1 Split plot data with whole plots arranged in randomized complete block design (hypothetical data) Block 1 2 3 Total Whole plot treatment W2 W1 split plot treatment split plot treatment Total s3 s2 s1 s2 s4 s1 s3 s4 3 6 6 15 4 10 10 24 7 1 4 12 6 11 4 21 20 28 24 72 2 3 8 10 21 2 8 8 18 1 2 9 12 14 18 13 45 Total 20 36 40 96 e Total and Means 1 S(split plot) (6 observations) Total Mean 36 6 42 7 8 24 4 Grand Total 168 66 11 Grand Mean 7 2 64 8 3 64 Model: W2 Y, , k l.J = 'j.L 96 + p, J 1-L = mean p. = effect of block j J 0 .. l.J Eijk -- W(whole plots) (12 observations) Total Mean W1 72 6 Blocks (8 observations) Total Mean 40 5 = = 8 + T,l. + 0 l.J .. + ak + (aT) , k + l. €, , k l.J T, = effect of whole plot i l. ak = effect of split plot k (aT) ik = effect of interaction of whole plot i and split plot k error (a) error (b) Analysis of Variance Source B (Blocks) w (whole plot treatments) BxW (error (a)) s (split plot treatments) sxw (interaction of S and W) (**} SxB:W (error (b)) Total (Corrected for mean) Mean Total (Uncorrected for mean} = = = = = = = = = (*) R(p 'j.L 1 T 1 a,aT) R(T 'j.L,p,a,aT) R(o 'j.L 1 p 1 T,a 1 aT) R(a 'j.L,p,T,aT) R(aTI!-L,a,T,p) R(Eiu.a TaT o) R(p,T,o,a,aT,EI!-L) R(l.l) R(u o.T o a,aT E) df 2 1 2 3 3 12 23 1 24 ss 48 24 16 156 84 112 440 1176 1616 (*)Notation follows that of Searle(1971); since the design is balanced, R(PIJ.l,T,a,aT) = R(pjJ.l), etc. The simpler notation is used later. (**) SxB:W means SxB within W. Calculations of sums of squares: N = 2•3•4 = 24 R(p,T,o,a,aT,eiJ.l) y = 7 = 1616- 1176 = 440 3 2 +64 2 +64 2 ) 8 - - 1176 R(pl~) = R(~,p) - R(~) = -( 40 R(TI~) = R(~ 1 T) - R(~) = -(72 12+96 2 R(o!~ 1 p 1 T) = R(o,~ 1 p 1 T) = R(aTI~,a,T) 2) - - 1176 R(aT 1 ~ 1 a 1 T) = 1440 R(el~,p,o,a,T,aT) = 1224 - 1176 48 = 1200- 1176 = 24 - R(~ 1 P) - R(T,~) + R(~) 1264 - 1224 - 1200 + 1176 = = = 16 - R(~,a) - R(~ 1 T) + R(~) 1332 - 1200 + 1176 = 84 = R(e,~,a,p,o,T,aT)- R(~ 1 p,T,5)- R(~,a,T,aT) = 1616 - 1264 - 1440 + 1200 = + 112 Data 5P-2 Data 5P-2: Data 5P-1 with the following covariate Z which varies with split plot Covariate (Z) 51 52 whole plot W1 Total 53 54 B1 1 2 1 2 6 2 0 2 4 8 B2 2 2 0 4 8 4 1 3 4 12 B3 3 5 2 0 10 3 2 4 7 16 Total 6 9 3 6 24 9 3 9 15 36 4 51 52 W2 53 54 Total R(T,~) Totals and Means W (whole plot) (12 observations) Total Mean 24 2.0 1 2 36 3.0 blocks (8 observations) Total Mean 1 14 14/8 2 20 20/8 3 26 26/8 Grand 2.5 Total 60 s (split plot) (6 observations) Total Mean 15 2. 5 12 2. 0 12 2. 0 21 3. 5 1 2 3 4 . . +ak+(aT) J..k+f3 1 (z l.J. .. -z • • • )+f3 2 (z l.J .. k-z l.J. .. )+c..l.J'k Model: Yijk = 11 +p.+T.+o J J. l.J P· = effect of jth block J ak = effect of kth split plot /32 = split plot regression slope T. = effect of ith whole plot J. /31 = whole plot regression slope 0 .. = error a c.ijk = error b l.J Table of sum of squares and products Source B .e yy 48 24 16 156 84 112 1176 1616 df 2 1 2 3 3 12 1 24 w BxW (error a) s sxw SxB:W (error b) Mean Total YZ 18 12 4 33 33 17 420 537 zz 9 6 1 9 21 20 150 216 yy column is the same as in SP-1, zz column is computed in the same fashion. Thus, only computations for YZ column are illustrated. 2 Totalyz Meanyz = NY Byz e 3 = }; 4 }; }; y .. k. z .. k i=1 j=1 k=1 l.J l.J = 3(1)+ 6(2)+···+ 14(4)+ 18(4)+ 13(7) = 537 ...z ... = 168•60 = 420 24 3 2 4 2 4 }; ( }; }; y .. k) ( }; }; j=1 i=1 k=1 l.J i=1 k=1 z.l.J'k) -420 40(14)+64(20)+64(26) 2•4 = 438 2 3 4 3 4 }; ( }; }; }; y .. k) ( }; z. 'k) j=1 k=1 l.J i=1 j=1 k=1 l.J WYZ = 3(4) 5 - 420 = 432 8 420 = 18 - 420 = 12 - 420 2 3 4 2: 2: ( 2: 4 y, 'k) ( 2: lJ = i=1 j=1 k=1 z. 'k) lJ k=1 - 438 - 432 + 420 4 = 454 - 438 - 432 + 420 = 4 3 2 2: Y. 'k) ( 2: i=1 1=1 j=1 lJ 2 ( . 2: 4 2: k=1 - 420 = 453 - 420 = 33 2(3) 2 4 3 2: 2: ( 2: i=1 k=1 3 y, 'k) ( 2: z. 'k) j=1 lJ j=1 lJ - 453 - 432 + 420 3 = 498 - 453 - 432 + 420 = 33 SxB:Wyz: 2 3 4 2: 2: 2: i=1 j=1 k=1 Y .. kz. 'k- 454 - 498 + 432 lJ lJ = 537 - 454 - 498 + 432 = 17 Analysis of Variance and Covariance Source B (block) w (whole plot treatment) Regression (a) = R(p ,J..L,T) = R(T ].1. 1 p,{3 1 ) = R(f3 1 IJ..L,p,T) BxW (error (a)) s s Regression (b) 16.0 = R(oi]J.,p ,T ,{3 1 ) 1 0.0 = R(a!J..L,p,T,aT,{3 2 ) 3 84.243 and W) = R(aTIJ..L,p,T,a,{3 2 ) = R(f3 2 !J..L,p,T,a,aT) 3 37.474 1 14.450 11 97.550 = R(ci]J.,p,a,T,aT,{3 2 ) SxB: w (error (b)) ss 48 3.4286 1 (split plot treatment) sxw (interaction of df 2 1 A {3 1 = BxWYZ I BxWZZ = 411 = 4 A {3 2 = SxB:Wyz 1 sxB:Wzz = 17120 = 0.85 6 The SS's adjusted by regression on Z are illustrated below: R(PI~> = 48, remains same since it is not of interest to adjust for Z on the blocks. = (12 + 4) 2 - (24 + 16) - 6 = -- 40 - 256 - 0 = + 1 = 40 - 256 = 3.4286 7 3.4286 7 = 42 = 16 1 = (156 + 112) - = 268 - 86.207 (33+17}- 2 9+20 = = 84 + 112 - Note: 181.793 <33 + 17 > 21+20 2 R(a,~l~,~ 2 ) and R(aT,~I~,a,T,~ 2 ) later use. 7 = 196 - 60.976 = 135.024 are intermediate steps for sxB:Wzz R(al~,p,T,aT,~ 2 ) = = = 14.450 20 R(a,cl~,p,T,aT,~ 2 ) = 135.024 - 97.55 - SS error b = 181.793 - 97.55 = 84.243 37.474 Data SP-3 Split plot data with plots arranged in a completely randomized design and a covariate z that is constant within the whole plot. (Winer, 1971, p. 803) whole plot Subject Split plots B1 B2 y z y Total y A1 1 2 3 4 10 15 20 12 8 12 14 6 3 5 8 2 18 27 34 18 5 6 7 8 Total Mean 15 25 20 15 132 16.5 10 20 15 10 95 11.9 1 8 10 2 39 4.88 25 45 35 25 227 A2 T. ~ ak = = A effect (whole plot) B effect (split plot) 0 .• l.J ~1 = = error (a) c. 'k = error (b) l.J whole plot regression slope e 8 4lt Analysis of variance and covariance Source A (whole plot) Regression Error (a) B (split plot) AxB (interaction) Error (b) ss df 1 1 5 1 1 6 R(T IJ.L,/31) = R(J3 1 IJ.L,T) = R(o I11 ,T,/3 1 ) = R(a!J.L,T,aT) = R(TaiJ.L,T,a) = RCc.lu,T,a,Ta) = 44.492 166.577 61.298 85.563 0.563 6.375 Table of SS and products Symbol w E(a) s ws E(b) &1 y2 ZY 12.38 163.00 0 0 0 68.06 227.88 85.563 0.563 6.375 z2 2.25 159.50 0 0 0 = 163.00 = 1.02 159.50 Since the computations are illustrated in Winer have omitted them here. (1971, p. 803-5) we References Federer. W.T. (1955), Experimental Design, Theory The Macmillan Co., New York, Chapter 16. and Application. Federer, W.T., and Henderson, H.V. (1979), Covariance Analysis of Designed Experiments X Statistical Packages: An Update, Proc., Comp. Sci. and Stat.: 12th Ann. Sym. on the Interface. GENSTAT b General Statistical Rothamsted Experimental Station. Searle, S.R., Program Release (1983), (1971), Linear Models, Wiley, N.Y., 532pp. Searle, S.R., Hudson, G.F.S., and Federer, W.T. (1985), Annotated Computer Output for Covariance-Text, BU-780-M, Biometrics Unit Mimeo Ser., Cornell University, Ithaca, NY. Winer, B.J., (1971), Statistical Principles in Experimental Design, McGraw-Hill Book Company, New York: 907pp. 9 SP-1 and SP-2: Control Language control Language is typed in upper case and comments are in bold face. REFE' SPLIT ~ file name 'UNITS' $ 24 ~number of observations 'FACTOR' BLOCKS $3 : PLOTS $2 } define levels of each factor 1 : SUBPLOTS $4 READ/FORM=P, PRIN=D' BLOCKS, PLOTS, SUBPLOTS, X, Y 'RUN' 1 1 1 1 1 1 1 1 1 1 2 1 2 3 4 1 1 2 1 2 2 ~ Input variables 3 4 7 6 3 1 2 2 0 2 1 2 3 2 1 1 2 4 4 14 2 1 1 2 6 2 1 2 2 10 2 1 3 0 1 2 1 4 4 11 2 2 2 2 3 3 3 3 2 2 2 2 1 1 1 1 1 2 3 4 1 2 3 4 4 1 3 4 3 5 2 0 8 8 2 18 6 10 4 4 3 2 1 3 10 3 2 2 2 8 3 2 3 4 9 3 2 4 7 13 1 EOD 1 ~ tell GENSTAT that data flow ends 'BLOCKS' BLOCKS/PLOTS/SUBPLOTS ~define error terms (strata) of a factorial model 'TREATMENTS' PLOTS*SUBPLOTS ~ treatment terms of a factorial model 1 COVARIATES 1 X ~covariate 'ANOVA' Y ~ invokes analysis of variance on Y variable 'RUN' 'STOP' 10 SP-3: Control Language OK, SLIST SPLIT3.0GEN 'REFE' SPLIT3 'UNITS' $ 16 'FACTOR' PLOT $2 : SUBPLOT $2 : SUBJECT $8 'READ/FORM=P, PRIN=D' SUBJECT, PLOT, SUBPLOT, Y, Z 'RUN' 1 1 1 10 3 1 1 2 8 3 2 1 1 15 5 2 1 2 12 5 3 1 1 20 8 3 1 2 14 8 4 1 1 12 2 4 1 2 6 2 5 2 1 15 5 2 2 10 6 2 1 25 6 2 2 20 7 2 1 20 7 2 2 15 8 2 1 15 8 2 2 10 1 1 8 8 10 10 2 2 'EOD' 'BLOCKS' PLOT/SUBJECT/SUBPLOT 'TREATMENT' PLOT*SUBPLOT 'COVARIATES' Z 'ANOVA' Y 'RUN' 'STOP' 11 SP-1: SP-2: Split plots with whole plots arranged in RCB design Split plots with whole plots arranged in RCB with a covariate with split plot Analysis of variance table on covariate Z ***** ANALYSIS OF VARIANCE ***** VARIATE: Z DF ss SS% MS BLOCKS STRATUM 2 9.000 13.64 4.500 BLOCKS.PLOTS STRATUM PLOTS RESIDUAL TOTAL 1 2 3 6.000 1.000 7.000 9.09 10.61 6.000 0.500 2.333 12.000 1. 52 BLOCKS.PLOTS.SUBPLOTS STRATUM SUBPLOTS 3 9.000 PLOTS.SUBPLOTS 3 21.000 RESIDUAL 12 20.000 TOTAL 50.000 18 13.64 31.82 30.30 75.76 3.000 7.000 1. 667 2.778 1. 800 4.200 SOURCE OF VARIATION GRAND TOTAL 23 66.000 GRAND MEAN 2.50 TOTAL NUMBER OF OBSERVATIONS 100.00 24 12 VR ANOVA for Y variable without covariate Z ***** ANALYSIS OF VARIANCE ***** VARIATE: Y SOURCE OF VARIATION ss DF MS SS% VR (F-statistics) 10.91 BLOCKS STRATUM 2 R(pi~,T,a,aT) 48.000 24.000 BLOCKS.PLOTS STRATUM PLOTS 1 R(TI~,p,a,aT) 24.000 5.45 24.000 3.000 16.000 8.000 40.000 13.333 3.64 RESIDUAL TOTAL 2 R(ol~,p,T,a,aT) 3 BLOCKS.PLOTS.SUBPLOTS STRATUM SUBPLOTS 3 R(al~,p,T,aT,O) PLOTS.SUBPLOTS RESIDUAL TOTAL GRAND TOTAL 156.000 52.000 84.000 28.000 12 R(EI~,a,T,aT,p,o)112.000 9.333 352.000 18 19.556 23 440.000 GRAND MEAN 7.00 TOTAL NUMBER OF OBSERVATIONS 24 13 9.09 35.45 5.571 19.09 3.000 25.45 80.00 100.00 = 24.00 8.00 ~**** ANALYSIS OF VARIANcr (ADJUSTED FOR COVARIATE) ***** VARIATE: Y SOURcr OF VARIATION ss DF MS SS'/. VR OOV EF = covariance efficiency factor (F-statislic) BLOCKS STRATUM COVARIATE RESIDUAL TOTAL 1 (*) pooled {36.000 1 12.000 18.000 2 R(p!Jl,T) BLOCKS.PLOTS STRATUM PLOTS COVARIATE 3. 429 16.000 R(T j,J, p./1 1 ) R{l1l j,t,p,T) o.ooo R(ol~.p.T,/1 1 ) RESIDUAL TOTAL 3 BLOCKS.PLOTS.SUBPLOTS STRATUM SUBPLOTS PLOTS.SUBPLOTS COVARIATE 19.129 RESIDUAL TOTAL 3 R(aljJ,p,T,aT,/12 ) 3 R(aTijJ,p,T,a,Jl2 ) 1 R{I12 11J,p,T,a,aT) 11 R(EhJ,p,a,T,ar,{}2 ) 18 GRAND TOTAL 23 GRAND MEAN TOTAL NUMBER OF OBSERVATIONS (*) 301. 146 7.00 24 Block is just a nuisance factor; hence only R(pj,t,T) = 18 is used in Analysis of variance 81.243 37.174 14.150 97.550 233.717 8.18 2.73 10.91 36.000 12.000 21.000 0.78 3.64 0.00 4.12 3.129 16.000 0.000 6.176 19.15 8.52 3.28 22.17 53.12 28.081 12.491 11.150 3.000 2.000 0.113 3.166 1.409 1.629 8.868 12.984 0.870 0.711 1.052 68.14 NOTE: low value of COY EF (usually close to unity) indicates high correlation between treatment and covariate e.g. COY EF for plots is .113; indicating correlation between wi and Zi(Wl = G, w2 = s. zl = 2, z2 = 3) 14 - - - ***** COVARIANCE REGRESSIONS ***** SE COEFFICIENT COVARIATE (Z) BLOCKS STRATUM ({3 0 is not of interest) z A 1.15 {30 = 2.0 Byz 18 = -- = 9 Bzz BLOCKS.PLOTS STRATUM " {31 = 4 z 0 BLOCKS.PLOTS.SUBPLOTS STRATUM A z 0.666 {32 = 0.85 ***** TABLES OF MEANS ***** (ADJUSTED FOR COVARIATE) -- VARIATE: Y GRAND MEAN 7.00 PLOTS 1 8.oo SUBPLOTS 2 A 6.oo = Y2 •• - f3 1 1 2 3 6.00 7.43 4.43 cz 2 •• - z... > - = 8-4.0(3-2.5)=6 4 1o.15 = Y.. 4 - 52 cz .. 4 - z... > !- = 11-0.85( 2 ~~) = 11-.85 = 10.15 SUBPLOTS PLOTS 1 2 3 4 1 7.00 9.15 6.85 9.00 2 5.00 5.70 2.00 11.3o = - 2.5) - 15 Y2 • 4 -5 1 cz 2 •• 15 .85(~ z... > -3) = 11.30 ***** STANDARD ERRORS OF DIFFERENCES OF MEANS ***** TABLE PLOTS SUBPLOTS REP SED 12 0.000 6 1. 844 PLOTS SUBPLOTS 3 2.718 ***** STRATUM STANDARD ERRORS AND COEFFICIENTS OF VARIATION ***** STRATUM DF SE CV% BLOCKS BLOCKS.PLOTS BLOCKS.PLOTS.SUBPLOTS 1 1 11 1. 225 17.5 0.0 42.5 0.000 2.978 2.978 = unadjusted standard error Jcov EF of Residual = ..../9.333 ..../1. 052 -- NOTE: A A ) S.E (Y i .. - y.. l •• A I ) = 0.0 W r = = 2Eb r(w) (1 + { = { 2{97.55} 3(2)(11) = { -r- = { 2{97.55} 3 ( 11) 2Eb Wzz I (w-1) BxW )}1/2 S 22 / (s-1) SxB:W )} 1/2 zz = A S.E (Y.l• k- yi•k') where { 2E r(:) A S.E (Y •• k - yo o k A = (1 + zz (1 + <1 + 9L{4-1} 20 = 1. 844 (S zz + SxW zz )/w(s-1) )}1/2 SxB:W zz (1 + {9+21}L{2} {3} >}1/2 20 no. of whole plot no. of blocks = 3 Eb = error b )}1/2 = = 2 97.55/11 16 = 2.718 S = no. of split plot Ea = error a = o = SP-3: Split plots with whole plot arranged in CRD with a covariate constant within whole plot ***** ANALYSIS OF VARIANCE ***** ANOVA on Covariate Z VARIATE: Z ss SS% 2.250E 1. 595E 1.618E 0 2 2 1. 39 98.61 100.00 PLOT. SUBJECT. SUBPLOT STRATUM SUBPLOT O.OOOE 1 PLOT . SUBPLOT 1 O.OOOE RESIDUAL O.OOOE 6 TOTAL 8 O.OOOE 0 0 0 0 0.00 0.00 GRAND TOTAL 2 100.00 SOURCE OF VARIATION PLOT.SUBJECT STRATUM PLOT RESIDUAL TOTAL e DF 1 6 7 15 1.618E GRAND MEAN 4.88 TOTAL NUMBER OF OBSERVATIONS o.oo o.oo MS VR 2.250E 2.658E 2.311E 0 1 1 0.085 O.OOOE O.OOOE O.OOOE O.OOOE 0 0 0 0 16 Notice that ss in plot.subject.subplot stratum are all zeroes since Z is constant within whole plot. ANOVA on Y without covariate Z ***** ANALYSIS OF VARIANCE ***** VARIATE: y SOURCE OF VARIATION PLOT.SUBJECT STRATUM PLOT RESIDUAL TOTAL DF ss SS% MS VR 1 6 7 68.063 227.875 295.938 17.52 58.66 76.19 68.063 37.979 42.277 1. 792 85.563 0.563 6.375 92.500 22.03 0.14 1. 64 23.81 85.563 0.563 1.063 11.563 80.529 0.529 388.438 100.00 PLOT. SUBJECT. SUBPLOT STRATUM SUBPLOT 1 PLOT.SUBPLOT 1 RESIDUAL 6 TOTAL 8 GRAND TOTAL e 15 GRAND MEAN 14.19 TOTAL NUI-1:BER OF OBSERVATIONS 16 17 Covariance Analysis ***** ANALYSIS OF VARIANCE (ADJUSTED FOR COVARIATE) *~*** VARIATE: Y ss SS"/. MS VR COV EF 272.367 14.492 166.577 12.260 38.910 3.629 13.587 7 11.45 12.88 15.78 70.12 0.986 1 R(P 1 1~.r) 5 R(o!Jl,T,/}l) 44.492 166.577 61.298 1 R(alrl,T,crr) 85.563 1 R(Tal~.r.a) 0.563 6 R{Ej~.T.a,Ta) 6.375 92.500 8 22.03 0.11 1.61 23.81 85.563 0.563 1.063 11.563 80.529 0.529 364.867 93.93 OF SOURCE OF VARIATION PLOT. SUBJECf STRATUM PLOT COVARIATE 1 RESIDUAL TOTAL PLOT. SUBJECf. SUBPLOT STRATUM SUBPLOT PLOT. SUBPLOT RF.SIDUAL TOTAL GRAND TOTAL 15 GRAND MEAN TOTAL NUMBER OF OBSERVATIONS ***** R(ri~.P 1 ) COVARIANCE REGRESSIONS 1.000 1.000 1.000 11.19 16 ~** COEFFICIENT COVARIATE 3.098 SE PLOT. SUBJECf STRATUM A z /}1 = 1.02 0.277 18 e e - ***** TABLES OF MEANS ***** (ADJUSTED FOR COVARIATE) VARIATE: Y GRAND MEAN PLOT 14.19 2 1 12.51 15.87 = Y2 • • - ~ 1 cz 2· tJ - z•• > = 16.25-1.02(5.25-4.88) = 15.87 SUBPLOT .e 1 16.50 2 SUBPLOT PLOT 1 2 1 14.63 10.38 2 18.37 13.37 = 11.88 same as unadjusted mean Y2 • 2 -~tJ 1 cz 2 • - z • • > = 13.75-1.02(5.25-4.88) = 13.37 ***** STANDARD ERRORS OF DIFFERENCES OF MEANS ***** TABLE PLOT SUBPLOT PLOT SUBPLOT REP 8 8 4 1.763 0.515 1.829 SED EXCEPT WHEN COMPARING MEANS WITH SAME LEVEL(S) OF: PLOT 0.731 ***** STRATUM STANDARD ERRORS AND COEFFICIENTS OF VARIATION ***** STRATUM DF SE CV% PLOT.SUBJECT 5 2.476 17.5 PLOT. SUBJECT. SUBPLOT 6 1. 031 = v'l. 063 7.3 v'l. 000 = [ residual MS of unadjusted )1/2 cov EF of adjusted residual 19