You can make different lm objects by adding all predictors and compare them with anova(lm1,lm2,lm3...). See if p value is not significant, the more complex model is not appropriate. Dr Suman Kumar -- View this message in context: http://r.789695.n4.nabble.com/SSEc-and-SSEr-tp4637855p4637963.html Sent from the R help mailing list archive at Nabble.com.