```Date: Mon, 24 May 1999 10:27:20 -0500 Reply-To: "Bauer, John" Sender: "SPSSX(r) Discussion" From: "Bauer, John" Subject: Re: new to glm, a couple of ?'s Craig, The sum of squares due to the intercept is calculated in the same way as the other sums of squares. Assuming you're working with the default, Type III sums of squares: First calculate the sum of squares due to the full model; then fit a reduced model, omitting the effect in question (in this case the intercept). The difference in the two model sums of squares is attributed to the effect in question (e.g. the intercept). Like MANOVA, GLM is also using listwise deletion when there are missing values. The fractional degrees of freedom are a consequence of the random effect in the design. They are computed using Satterthwaite's approximation. The references below are only for Sattertwaite's approximation; perhaps someone else can suggest a 'good' reference on the use of SPSS GLM. John Bauer, Ph.D. SPSS Support Statistician REFERENCES SPSS 7.5 Statistical Algorithms, pp. 260-262 Satterthwaite, F. E. 1946. An approximate distribution of estimates of variance components. Biometrics Bulletin, 2: 110-114. -----Original Message----- From: craig enders [mailto:cenders@UNLINFO.UNL.EDU] Sent: Monday, May 24, 1999 8:22 AM To: SPSSX-L@UGA.CC.UGA.EDU Subject: new to glm, a couple of ?'s I am trying to convert from using manova to glm and have a couple of questions about the glm output/calculations. First, a simple one. In running a simple one-way anova in glm you get a sum of squares value for the intercept term. How is that being calculated? Second, I was running a mixed design that had a couple of missing data points. In manova, these points were excluded and I was left with only cases that had complete data in all cells. However, in running the same analysis under glm I got slightly different results -- the df were not integers. Unfortunately, I cannot remember if it was the between or within factor that was affected (I think it was the within). What is the difference in the calculations under glm when there are missing observations? Also, if anyone could provide me a good reference material on glm I would appreciate it. Thanks in advance, Craig Enders -- Craig Enders cenders@unlinfo.unl.edu ```

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