Unequal n example from Neter Wasserman & Kutner, p.763, 768 MTB > name c1 'sex' c2 'devpt' c3 'observat' c4 'growth' MTB > read c1-c4 DATA> 1 1 1 1.4 DATA> 1 1 2 2.4 DATA> 1 1 3 2.2 DATA> 2 1 1 2.4 DATA> 1 2 1 2.1 DATA> 1 2 2 1.7 DATA> 2 2 1 2.5 DATA> 2 2 2 1.8 DATA> 2 2 3 2.0 DATA> 1 3 1 0.7 DATA> 1 3 2 1.1 DATA> 2 3 1 0.5 DATA> 2 3 2 0.9 DATA> 2 3 3 1.3 DATA> end 14 ROWS READ ******RUN GLM Solution for Unbalanced Design MTver7 manual 8-27 MTB > glm growth = sex | devpt Factor Levels Values sex 2 1 2 devpt 3 1 2 3 Analysis of Variance for growth Source DF Seq SS Adj SS Adj MS F sex 1 0.0029 0.1200 0.1200 0.74 devpt 2 4.3960 4.1897 2.0949 12.89 sex*devpt 2 0.0754 0.0754 0.0377 0.23 Error 8 1.3000 1.3000 0.1625 Total 13 5.7743 Unusual Observations for growth Obs. growth Fit Stdev.Fit Residual St.Resid 4 2.40000 2.40000 0.40311 0.00000 * X X denotes an obs. whose X value gives it large influence. ********************************************* note: these agree with NWK pg. 753 Table 20.4 Adj SS, MS, test statistics ******************************************** MTB > glm growth = devpt | sex Factor Levels Values devpt 3 1 2 3 sex 2 1 2 Analysis of Variance for growth Source DF Seq SS Adj SS Adj MS F devpt 2 4.3063 4.1897 2.0949 12.89 sex 1 0.0926 0.1200 0.1200 0.74 devpt*sex 2 0.0754 0.0754 0.0377 0.23 Error 8 1.3000 1.3000 0.1625 Total 13 5.7743 Unusual Observations for growth Obs. growth Fit Stdev.Fit Residual St.Resid 4 2.40000 2.40000 0.40311 0.00000 * X X denotes an obs. whose X value gives it large influence. ------------------------------------------------------------------------- NOW CONSIDER APPROXIMATE SOLUTION FROM MILLER-- 2-way on cell means 2.0 1 1 1.9 1 2 0.9 1 3 2.4 2 1 2.1 2 2 0.9 2 3 TWOWAY on CELL MEANS for APPROX Procedure MTB > twoway c1, c2 c3 ANALYSIS OF VARIANCE C1 SOURCE DF SS MS C2 1 0.0600 0.0600 C3 2 1.9600 0.9800 ERROR 2 0.0400 0.0200 TOTAL 5 2.0600 MTB > note ERROR is really interaction Here are the points of difference between Miller's approximate solutions and the glm exact one. GLM shows very clearly (by looking at the sequential sums of squares) that the order of entering the factor makes a difference. Thus for comparison we look at the adjusted sums of squares in the glm runs: MILLER GLM SS MS Source SS(Adj) MS(Adj) 0.12 0.12 Gender 0.1200 0.1200 3.92 1.96 Development 4.1897 2.0949 0.08 0.04 Interaction 0.0754 0.0377 The differences are small, and the F-tests yield the same conclusions.