search for: math_1

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2009 Oct 21
3
Missing data and LME models and diagnostic plots
Hello Running R2.9.2 on Windows XP I am puzzled by the performance of LME in situations where there are missing data. As I understand it, one of the strengths of this sort of model is how well it deals with missing data, yet lme requires nonmissing data. Thus, m1.mod1 <- lme(fixed = math_1 ~ I(year-2007.5)*TFC_, data = long, random = ~I(year-2007.5)|schoolnum) causes an error in na.fail.default, but adding na.action = "na.omit" makes a model with no errors. However, if I create that model, i.e. m1.mod1 <- lme(fixed = math_1 ~ I(year-200...
2009 Oct 21
1
Question on mixed effect models with LME
Good afternoon Using R 2.9.2 on a machine running Windows XP I have a longitudinal data set, with data on schools and their test scores over a four year period. I have centered year, and run the following m1.mod1 <- lme(fixed = math_1 ~ I(year-2007.5)*TFC_, data = long, random = ~I(year-2007.5)|schoolnum, na.action = "na.omit") where math_1 is a percentage of students in a given school that are at the lowest math achievement level, year is year, TFC_ is a categorical variab...